Variable magnification optical system, optical apparatus, and method for producing variable magnification optical system

ABSTRACT

A variable magnification optical system comprising, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a rear lens group having positive refractive power; upon varying a magnification, a distance between the first lens group and the second lens group being varied, a distance between the second lens group and the third lens group being varied, and a distance between the third lens group and the rear lens group being varied; the rear lens group comprising a focusing lens group which is moved upon carrying out focusing from an infinitely distant object to a closely distant object; and predetermined conditional expression(s) being satisfied, thereby various aberrations being corrected superbly.

TECHNICAL FIELD

The present invention relates to a variable magnification opticalsystem, an optical apparatus and a method for manufacturing the variablemagnification optical system.

BACKGROUND ART

There has been proposed a variable magnification optical system that issmall in size but can adopt large-sized image pick-up device suitablefor photo-taking a motion picture and for effecting high speed focusing.For example, refer to Japanese Patent application Laid-Open Gazette No.2015-064492. However, in the conventional variable magnification opticalsystem, corrections of various aberrations have not been madesufficiently.

PRIOR ART REFERENCE Patent Document

Patent Document 1: Japanese Patent application Laid-Open Gazette No.2015-064492.

SUMMARY OF THE INVENTION

The present invention is related to a variable magnification opticalsystem comprising, in order from an object side, a first lens grouphaving positive refractive power, a second lens group having negativerefractive power, a third lens group having positive refractive power,and a rear lens group having positive refractive power;

upon varying a magnification, a distance between said first lens groupand said second lens group being varied, a distance between said secondlens group and said third lens group being varied, and a distancebetween said third lens group and said rear lens group being varied;

said rear lens group comprising a focusing lens group which is movedupon carrying out focusing; and

the following conditional expressions being satisfied:

−1.00<f3f/f3r<−0.0500

0.100<BFw/fw<1.00

where f3f denotes a focal length of a most image plane side negativelens component in said third lens group; f3r denotes a composite focallength of lens components disposed on a side which is closer to theobject than said most image plane side negative lens component, in saidthird lens group; BFw denotes a back focus of said variablemagnification optical system in a wide angle end state; and fw denotes afocal length of said variable magnification optical system in the wideangle end state.

Further, the present invention is related to a method for manufacturinga variable magnification optical system comprising, in order from anobject side, a first lens group having positive refractive power, asecond lens group having negative refractive power, a third lens grouphaving positive refractive power, and a rear lens group having positiverefractive power; the method comprising the steps of:

constructing such that, upon varying a magnification, a distance betweensaid first lens group and said second lens group is varied, a distancebetween said second lens group and said third lens group is varied, anda distance between said third lens group and said rear lens group isvaried;

constructing such that said rear lens group comprises a focusing lensgroup which is moved upon carrying out focusing; and constructing suchthat the following conditional expressions are satisfied:

−1.00<f3f/f3r<−0.0500

0.100<BFw/fw<1.00

where f3f denotes a focal length of a most image plane side negativelens component in said third lens group; f3r denotes a composite focallength of lens components disposed on a side which is closer to theobject than said most image plane side negative lens component, in saidthird lens group; BFw denotes a back focus of said variablemagnification optical system in a wide angle end state; and fw denotes afocal length of said variable magnification optical system in the wideangle end state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A, FIG. 1B and FIG. 1C are cross sectional views in the wide angleend state, in the intermediate focal length state and in the telephotoend state, respectively, of a variable magnification optical systemaccording to a First Example.

FIG. 2A, FIGS. 2B and 2C are graphs showing various aberrations, uponfocusing on an infinite distance object, in the wide angle end state, inthe intermediate focal length state, and in the telephoto end state,respectively, of the variable magnification optical system according tothe First Example

FIG. 3A, FIG. 3B and FIG. 3C are graphs showing various aberrations,upon focusing on a close distance object, in the wide angle end state,in the intermediate focal length state, and in the telephoto end state,respectively, of the variable magnification optical system according tothe First Example.

FIG. 4A, FIG. 4B and FIG. 4C are cross sectional views in the wide angleend state, in the intermediate focal length state and in the telephotoend state, respectively, of a variable magnification optical systemaccording to a Second Example.

FIG. 5A, FIG. 5B and FIG. 5C are graphs showing various aberrations,upon focusing on an infinite distance object, in the wide angle endstate, in the intermediate focal length state, and in the telephoto endstate, respectively, of the variable magnification optical systemaccording to the Second Example.

FIG. 6A, FIG. 6B and FIG. 6C are graphs showing various aberrations,upon focusing on a close distance object, in the wide angle end state,in the intermediate focal length state and in the telephoto end state,respectively, of the variable magnification optical system according tothe Second Example.

FIG. 7A, FIG. 7B and FIG. 7C are cross sectional views in the wide angleend state, in the intermediate focal length state and in the telephotoend state, respectively, of a variable magnification optical systemaccording to a Third Example.

FIG. 8A, FIG. 8B and FIG. 8C are graphs showing various aberrations,upon focusing on an infinite distance object, in the wide angle endstate, in the intermediate focal length state, and in the telephoto endstate, respectively, of the variable magnification optical systemaccording to the Third Example.

FIG. 9A, FIG. 9B and FIG. 9C are graphs showing various aberrations,upon focusing on a close distance object, in the wide angle end state,in the intermediate focal length state and in the telephoto end state,respectively, of the variable magnification optical system according tothe Third Example.

FIG. 10A, FIG. 10B and FIG. 10C are cross sectional views in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, respectively, of a variable magnification opticalsystem according to a Fourth Example.

FIG. 11A, FIG. 11B and FIG. 11C are graphs showing various aberrations,upon focusing on an infinite distance object, in the wide angle endstate, in the intermediate focal length state and in the telephoto endstate, respectively, of the variable magnification optical systemaccording to the Fourth Example.

FIG. 12A, FIG. 12B and FIG. 12C are graphs showing various aberrations,upon focusing on a close distance object, in the wide angle end state,in the intermediate focal length state and in the telephoto end state,respectively, of the variable magnification optical system according tothe Fourth Example.

FIG. 13A, FIG. 13B and FIG. 13C are cross sectional views in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, respectively, of a variable magnification opticalsystem according to a Fifth Example.

FIG. 14A, FIG. 14B and FIG. 14C are graphs showing various aberrations,upon focusing on an infinite distance object, in the wide angle endstate, in the intermediate focal length state and in the telephoto endstate, respectively, of the variable magnification optical systemaccording to the Fifth Example.

FIG. 15A, FIG. 15B and FIG. 15C are graphs showing various aberrations,upon focusing on a close distance object, in the wide angle end state,in the intermediate focal length state and in the telephoto end state,respectively, of the variable magnification optical system according tothe Fifth Example.

FIG. 16A, FIG. 16B and FIG. 16C are cross sectional views in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, respectively, of a variable magnification opticalsystem according to a Sixth Example.

FIG. 17A, FIG. 17B and FIG. 17C are graphs showing various aberrations,upon focusing on an infinite distance object, in the wide angle endstate, in the intermediate focal length state and in the telephoto endstate, respectively, of the variable magnification optical systemaccording to the Sixth Example.

FIG. 18A, FIG. 18B and FIG. 18C are graphs showing various aberrations,upon focusing on a close distance object, in the wide angle end state,in the intermediate focal length state and in the telephoto end state,respectively, of the variable magnification optical system according tothe Sixth Example.

FIG. 19A, FIG. 19B and FIG. 19C are cross sectional views in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, respectively, of a variable magnification opticalsystem according to a Seventh Example.

FIG. 20A, FIG. 20B and FIG. 20C are graphs showing various aberrations,upon focusing on an infinite distance object, in the wide angle endstate, in the intermediate focal length state and in the telephoto endstate, respectively, of the variable magnification optical systemaccording to the Seventh Example.

FIG. 21A, FIG. 21B and FIG. 21C are graphs showing various aberrations,upon focusing on a close distance object, in the wide angle end state,in the intermediate focal length state, and in the telephoto end state,respectively, of the variable magnification optical system according tothe Seventh Example.

FIG. 22A, FIG. 22B and FIG. 22C are cross sectional views in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, respectively, of a variable magnification opticalsystem according to an Eighth Example.

FIG. 23A, FIG. 23B and FIG. 23C are graphs showing various aberrations,upon focusing on an infinite distance object, in the wide angle endstate, in the intermediate focal length state and in the telephoto endstate, respectively, of the variable magnification optical systemaccording to the Eighth Example.

FIG. 24A, FIG. 24B and FIG. 24C are graphs showing various aberrations,upon focusing on a close distance object, in the wide angle end state,in the intermediate focal length state, and in the telephoto end state,respectively, of the variable magnification optical system according tothe Eighth Example.

FIG. 25 is a view showing a configuration of a camera equipped with thevariable magnification optical system.

FIG. 26 is a flowchart schematically showing a method for manufacturingthe variable magnification optical system.

EMBODIMENT FOR CARRYING OUT THE INVENTION

Hereinafter, a variable magnification optical system according to thepresent embodiment, an optical apparatus and a method for manufacturingthe variable magnification optical system, will be explained. At first,the variable magnification optical system according to the presentembodiment will be explained.

The variable magnification optical system according to the presentembodiment comprises, in order from an object side, a first lens grouphaving positive refractive power, a second lens group having negativerefractive power, a third lens group having positive refractive power,and a rear lens group having positive refractive power;

upon varying a magnification from a wide angle end state to a telephotoend state, a distance between said first lens group and said second lensgroup being varied, a distance between said second lens group and saidthird lens group being varied, and a distance between said third lensgroup and said rear lens group being varied;

said rear lens group comprising a focusing lens group which is movedupon carrying out focusing from an infinite distance object to a closedistance object; and the following conditional expressions (1) and (2)being satisfied:

−1.00<f3f/f3r<−0.0500  (1)

0.100<BFw/fw<1.00  (2)

where f3f denotes a focal length of a most image plane side negativelens component in said third lens group; f3r denotes a composite focallength of lens components disposed on a side which is closer to theobject than said most image plane side negative lens component, in saidthird lens group; BFw denotes a back focus of said variablemagnification optical system in a wide angle end state; and fw denotes afocal length of said variable magnification optical system in the wideangle end state.

In the present embodiment, the rear lens group of the variablemagnification optical system according to the present embodimentcomprises at least two lens groups. Meanwhile, in the presentembodiment, a lens group means a portion which comprises at least onelens separated by an air space. Further, in the present embodiment, alens component means a single lens or a cemented lens composed of two ormore lenses cemented with each other.

The variable magnification optical system according to the presentembodiment can conduct superbly aberration corrections upon varying amagnification, by varying distances between the respective lens groupsupon varying a magnification from a wide angle end state to a telephotoend state. Further, the focusing lens group may be made compact andreduced in weight by disposing the focusing lens group in the rear lensgroup, and as a result, high speed focusing becomes possible and thevariable magnification optical system and the lens barrel can besmall-sized.

The conditional expression (1) defines a ratio of a focal length of amost image plane side negative lens component in the third lens group toa composite focal length of lens components disposed on a side which iscloser to the object than the most image plane side negative lenscomponent in the third lens group. With satisfying the conditionalexpression (1), the variable magnification optical system according tothe present embodiment can correct superbly spherical aberration andastigmatism.

When the value of f3f/f3r is equal to or exceeds the upper limit of theconditional expression (1), refractive power of the most image planeside negative lens component in the third lens group increases relativeto refractive power of lens components disposed on the side which iscloser to the object than the most image plane side negative lenscomponent in the third lens group, and it becomes difficult to correctsuperbly spherical aberration in a telephoto end state. Meanwhile, inorder to secure the effect of the present embodiment more surely, it ispreferable to set the upper limit value of the conditional expression(1) to −0.100. In order to secure the effect of the present embodimentmuch more surely, it is preferable to set the upper limit value of theconditional expression (1) to −0.150 and much more preferable to −0.190.

On the other hand, when the value of f3f/f3r is equal to or falls belowthe lower limit of the conditional expression (1), refractive power oflens components disposed on the side which is closer to the object thanthe most image plane side negative lens component in the third lensgroup increases relative to the refractive power of the most image planeside negative lens component in the third lens group, and it becomesdifficult to correct superbly astigmatism in the wide angle end state.Meanwhile, in order to secure the effect of the present embodiment moresurely, it is preferable to set the lower limit value of the conditionalexpression (1) to −0.800. In order to secure the advantageous effect ofthe present embodiment—much more surely, it is preferable to set thelower limit value of the conditional expression (1) to −0.700, morepreferable to −0.600, much more preferable to −0.550 and—much more andmore preferable to −0.500.

The conditional expression (2) defines a ratio of a back focus of thevariable magnification optical system in the wide angle end state and afocal length of the variable magnification optical system in the wideangle end state.

With satisfying the conditional expression (2), the variablemagnification optical system according to the present embodiment cancorrect superbly a coma aberration and other various aberrations in thewide angle end state. Meanwhile, by the term “back focus” is meant adistance from the most image side lens surface to the image plane on theoptical axis.

When the value of BFw/fw is equal to or exceeds the upper limit of theconditional expression (2), the back focus of the variable magnificationoptical system in the wide angle end state relative to the focal lengthof the variable magnification optical system in the wide angle end statebecomes large and it becomes difficult to correct superbly variousaberrations in the wide angle end state. Meanwhile, in order to attainthe advantageous effect of the present embodiment more surely, it ispreferable to set the upper limit value of the conditional expression(2) to 0.91. Further, in order to attain the advantageous effect of thepresent embodiment much more surely, it is preferable to set the upperlimit value of the conditional expression (2) to 0.85. and much morepreferable to 0.80.

On the other hand, when the value of BFw/fw is equal to or falls belowthe lower limit of the conditional expression (2), the back focus of thevariable magnification optical system in the wide angle end staterelative to the focal length of the variable magnification opticalsystem in the wide angle end state becomes small, and it becomesdifficult to correct various aberrations in the wide angle end state,and in particular coma aberration superbly. Meanwhile, in order tosecure the advantageous effect of the present embodiment more surely, itis preferable to set the lower limit value of the conditional expression(2) to 0.300. In order to secure the advantageous effect of the presentembodiment much more surely, it is preferable to set the lower limitvalue of the conditional expression (2) to 0.400 and more preferable to0.500.

Incidentally, in the conditional expression (2), “back focus of thevariable magnification optical system in the wide angle end state”denoted by BFw may be made “back focus of the variable magnificationoptical system in the state where the whole length is smallest”, and“focal length of the variable magnification optical system in the wideangle end state” denoted by fw may be “focal length of the variablemagnification optical system in the state where the whole length issmallest”. That is to say, the conditional expression (2) may beexpressed, as below:

0.100<BFs/fs<1.00  (2)

where BFs denotes a back focus of said variable magnification opticalsystem in a state where the whole length is smallest, and fs denotes afocal length of said variable magnification optical system in the statewhere the whole length is smallest.

By the above-mentioned configuration, the variable magnification opticalsystem according to the present embodiment can be small-sized but bemade compatible with a large sized imaging device, so the variablemagnification optical system which can correct superbly variousaberrations upon varying magnification and upon carrying out focusingcan be realized.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(3) is satisfied:

2.00<f1/fw<8.000  (3)

where f1 denotes a focal length of the first lens group, and fw denotesa focal length of the variable magnification optical system in the wideangle end state.

The conditional expression (3) defines a ratio of the focal length ofthe first lens group to the focal length of the variable magnificationoptical system in the wide angle end state. With satisfying theconditional expression (3), the variable magnification optical systemaccording to the present embodiment can correct superbly coma aberrationand other various aberrations in the wide angle end state.

When the value of f1/fw is equal to or exceeds the upper limit value ofthe conditional expression (3) of the variable magnification opticalsystem according to the present embodiment, refractive power of thefirst lens group becomes small, and it becomes difficult to correctsuperbly various aberrations in the wide angle end state. Meanwhile, inorder to secure the advantageous effect of the present embodiment moresurely, it is preferable to set the upper limit value of the conditionalexpression (3) to 7.000, and further in order to secure the advantageouseffect of the present embodiment much more surely, it is preferable toset the upper limit value of the conditional expression (3) to 6.500,and more preferable to 6.000.

On the other hand, when the value of f1/fw in the conditional expression(3) of the variable magnification optical system according to thepresent embodiment, is equal to or falls below the lower limit value,refractive power of the first lens group becomes large, and it becomesdifficult to correct various aberrations in the wide angle end state,and in particular coma aberration. Meanwhile, in order to secure theadvantageous effect of the present embodiment more surely, it ispreferable to set the lower limit value of the conditional expression(3) to 3.00. Further, in order to secure the advantageous effect of thepresent embodiment more surely, it is preferable to set the lower limitvalue of the conditional expression (3) to 4.00, and more preferable to4.50.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(4) is satisfied:

0.040<βFw<0.800  (4)

where βFw denotes a transverse magnification of the focusing lens groupin the wide angle end state.

The conditional expression (4) defines a transverse magnification of thefocusing lens group in the wide angle end state. With satisfying theconditional expression (4), the variable magnification optical systemaccording to the present embodiment can make amount of movement of thefocusing lens group upon focusing small so that the variablemagnification optical system can be made small-sized.

When the value of βFw is equal to or exceeds the upper limit value ofthe conditional expression (4) of the variable magnification opticalsystem according to the present embodiment, the amount of movement ofthe focusing lens group upon focusing becomes large, so it becomesdifficult to make the variable magnification optical system small-sized.Meanwhile, in order to secure the advantageous effect of the presentembodiment surely, it is preferable to set the upper limit value of theconditional expression (4) to 0.770. Further, in order to secure theadvantageous effect of the present embodiment much more surely, it ispreferable to set the upper limit value of the conditional expression(4) to 0.750, and more preferable to 0.730.

On the other hand, when the value of βFw in the conditional expression(4) of the variable magnification optical system according to thepresent embodiment, is equal to or falls below the lower limit value,sensitivity becomes high and the amount of movement of the focusing lensgroup upon focusing becomes small, so it becomes difficult to controlfocusing.

Meanwhile, in order to secure the advantageous effect of the presentembodiment more surely it is preferable to set the lower limit value ofthe conditional expression (4) to 0.200. Further, in order to secure theadvantageous effect of the present embodiment much more surely, it ispreferable to set the lower limit value of the conditional expression(4) to 0.300 and more preferable to 0.400.

It is desirable that, in the variable magnification optical systemaccording to the present embodiment, the rear lens group comprises afourth lens group having positive refractive power and a fifth lensgroup having negative refractive power and satisfies the followingconditional expression (5):

−3.000<f5/f3<−0.500  (5)

where f3 denotes a focal length of the third lens group, and f5 denotesa focal length of the fifth lens group.

The conditional expression (5) defines a ratio of the focal length ofthe fifth lens group to the focal length of the third lens group.

With satisfying the conditional expression (5), the variablemagnification optical system according to the present embodiment canmaintain power ratio between the third lens group and the fifth lensgroup properly and correct superbly astigmatism and coma aberration.

When the value of f5/f3 is equal to or exceeds the upper limit value ofthe conditional expression (5) of the variable magnification opticalsystem according to the present embodiment, refractive power of thethird lens group relative to refractive power of the fifth lens groupbecomes large and it becomes difficult to correct various aberrations inthe wide angle end state and in particular astigmatism superbly.Meanwhile, in order to secure the advantageous effect of the presentembodiment more surely, it is preferable to set the upper limit value ofthe conditional expression (5) to −0.800. In order to secure theadvantageous effect of the present embodiment much more surely, it ispreferable to set the upper limit value of the conditional expression(5) to −1.000, and more preferable to −1.100.

On the other hand, when the value of f5/f3 in the conditional expression(5) of the variable magnification optical system according to thepresent embodiment, is equal to or falls below the lower limit value,refractive power of the fifth lens group relative to refractive power ofthe third lens group becomes large, and it becomes difficult to correctvarious aberrations in the telephoto end state, and in particular comaaberration superbly. Meanwhile, in order to secure the advantageouseffect of the present embodiment more surely, it is preferable to setthe lower limit value of the conditional expression (5) to −2.500.Further, in order to secure the advantageous effect of the presentembodiment much more surely, it is preferable to set the lower limitvalue of the conditional expression (5) to −2.000, and more preferableto −1.400.

Further, it is desirable that, in the variable magnification opticalsystem according to the present embodiment, the fourth lens groupcomprises a focusing lens group. With such a configuration, in thevariable magnification optical system according to the presentembodiment, the focusing lens group may be small in size and light inweight, and as a result the variable magnification optical system and alens barrel can be made small in size.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(6) is satisfied:

4.000<f1/f1Rw<9.000  (6)

where f1 denotes the focal length of the first lens group, and f1Rwdenotes a composite focal length of lens groups in the wide angle endstate disposed on the side which is closer to the image plane than thefirst lens group.

The conditional expression (6) defines a ratio of the focal length ofthe first lens group relative to the composite focal length of lensgroups in the wide angle end state disposed on the side which is closerto the image plane—than the first lens group. With satisfying theconditional expression (6), the variable magnification optical systemaccording to the present embodiment can correct superbly coma aberrationand other various aberrations in the wide angle end state. Further, withsatisfying the conditional expression (6), variations in sphericalaberration and other various aberrations can be suppressed upon varyingmagnification from the wide angle end state to the telephoto end state.

When the value of f1/f1Rw is equal to or exceeds the upper limit valueof the conditional expression (6) of the variable magnification opticalsystem according to the present embodiment, refractive power of the lensgroups in the wide angle end state disposed on the side which is closerto the image plane than the first lens group, becomes large, and itbecomes difficult to correct various aberrations in the wide angle endstate and, in particular, coma aberration superbly. Further, uponvarying magnification from the wide angle end state to the telephoto endstate, it becomes difficult to suppress variations in sphericalaberration and in other various aberrations. Meanwhile, in order tosecure the advantageous effect of the present embodiment more surely, itis preferable to set the upper limit value of the conditional expression(6) to 8.500. Further, in order to secure the advantageous effect of thepresent embodiment much more surely, it is preferable to set the upperlimit value of the conditional expression (6) to 8.000, and morepreferable to 6.500.

On the other hand, when the value of f1/f1Rw in the conditionalexpression (6) of the variable magnification optical system according tothe present embodiment, is equal to or falls below the lower limitvalue, refractive power of the first lens group becomes large, and itbecomes difficult to correct various aberrations in the wide angle endstate and in particular coma aberration superbly. Further, upon varyingmagnification from the wide angle end state to the telephoto end state,it becomes difficult to suppress variations in spherical aberration andin other various aberrations. Meanwhile, in order to secure theadvantageous effect of the variable magnification optical systemaccording to the present embodiment more surely, it is preferable to setthe lower limit value of the conditional expression (6) to 5.000. And inorder to secure the advantageous effect of the present embodiment muchmore surely, it is preferable to set the lower limit value of theconditional expression (6) to 5.100, and more preferable to 5.200.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(7) is satisfied:

nd3fp<1.800  (7)

where nd3fp denotes refractive index of a lens having the largestrefractive index in the third lens group.

The conditional expression (7) defines refractive index of the lenshaving the largest refractive index in the third lens group. With usingglass material having high refractive index satisfying the conditionalexpression (7), the variable magnification optical system according tothe present embodiment can correct superbly longitudinal chromaticaberration and spherical aberration.

When the value of nd3fp is equal to or exceeds the upper limit value ofthe conditional expression (7) of the variable magnification opticalsystem according to the present embodiment, refractive power of thethird lens group becomes large, and it becomes difficult to correctsuperbly longitudinal chromatic aberration and spherical aberration.Meanwhile, in order to secure the advantageous effect of the presentembodiment more surely, it is preferable to set the upper limit value ofthe conditional expression (7) to 1.750. Further, in order to secure theadvantageous effect of the present embodiment much more surely, it ispreferable to set the upper limit value of the conditional expression(7) to 1.700, and more preferable to 1.650.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(8) is satisfied:

50.000<vd3p  (8)

where vd3p denotes Abbe's number of a lens having the smallest Abbe'snumber in the third lens group.

The conditional expression (8) defines Abbe's number of the lens havingthe smallest Abbe's number in the third lens group. With using glassmaterial of low dispersion satisfying the conditional expression (8),the variable magnification optical system according to the presentembodiment can let the third lens group have anomalous dispersion, andit becomes possible to correct superbly longitudinal chromaticaberration and spherical aberration.

When the value of vd3p in the conditional expression (8) of the variablemagnification optical system according to the present embodiment, isequal to or falls below the lower limit value, it is not possible to letthe third lens group have sufficient anomalous dispersion, and itbecomes difficult to correct superbly longitudinal chromatic aberrationand spherical aberration. Meanwhile, in order to secure the advantageouseffect of the present embodiment more surely, it is preferable to setthe lower limit value of the conditional expression (8) to 55.000. And,in order to secure the advantageous effect of the present embodimentmuch more surely, it is preferable to set the lower limit value of theconditional expression (8) to 58.000, and more preferable to 60.000.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(9) is satisfied:

0.500<1/βRw<1.000  (9)

where βRw denotes transverse magnification of a lens group disposed onthe most image plane side in the wide angle end state.

The conditional expression (9) defines the transverse magnification ofthe lens group disposed on the most image plane side in the wide angleend state. With satisfying the conditional expression (9), the variablemagnification optical system according to the present embodiment cancorrect superbly astigmatism and other various aberrations in the wideangle end state.

When the value of 1/βRw is equal to or exceeds the upper limit value ofthe conditional expression (9) of the variable magnification opticalsystem according to the present embodiment, the transverse magnificationof the lens group disposed on the most image plane side in the wideangle end state, becomes small, and it becomes difficult to correctsuperbly various aberrations in the wide angle end state and, inparticular, astigmatism. Meanwhile, in order to secure the advantageouseffect of the present embodiment more surely, it is preferable to setthe upper limit value of the conditional expression (9) to 0.950.Further, in order to secure the advantageous effect of the presentembodiment much more surely, it is preferable to set the upper limitvalue of the conditional expression (9) to 0.900, and more preferable to0.850.

On the other hand, when the value of 1/βRw in the conditional expression(9) of the variable magnification optical system according to thepresent embodiment, is equal to or falls below the lower limit value,the transverse magnification of the lens group disposed on the mostimage plane side in the wide angle end state, becomes large, andcurvature of field is apt to be generated in the wide angle end state,and further it becomes difficult to correct superbly variousaberrations. Meanwhile, in order to secure the advantageous effect ofthe variable magnification optical system according to the presentembodiment more surely, it is preferable to set the lower limit value ofthe conditional expression (9) to 0.550. And in order to secure theadvantageous effect of the present embodiment much more surely, it ispreferable to set the lower limit value of the conditional expression(9) to 0.600, and more preferable to 0.650.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(10) is satisfied:

0.500<f2fn/f2<1.100  (10)

where f2fn denotes a focal length of a most object side lens componentin the second lens group, and f2 denotes a focal length of the secondlens group.

The conditional expression (10) defines a ratio of the focal length ofthe most object side lens component in the second lens group relative tothe focal length of the second lens group. With satisfying theconditional expression (10), the variable magnification optical systemaccording to the present embodiment can arrange power of the most objectside lens component in the second lens group properly, so that it ispossible to correct superbly spherical aberration and other variousaberrations.

When the value of f2fn/f2 is equal to or exceeds the upper limit valueof the conditional expression (10) of the variable magnification opticalsystem according to the present embodiment, refractive power of the mostobject side lens component in the second lens group becomes small, andit becomes difficult to correct superbly spherical aberration and othervarious aberrations. Meanwhile, in order to secure the advantageouseffect of the present embodiment more surely, it is preferable to setthe upper limit value of the conditional expression (10) to 1.000.Further, in order to secure the advantageous effect of the presentembodiment much more surely, it is preferable to set the upper limitvalue of the conditional expression (10) to 0.900, and more preferableto 0.850.

On the other hand, when the value of f2fn/f2 in the conditionalexpression (10) of the variable magnification optical system accordingto the present embodiment, is equal to or falls below the lower limitvalue, refractive power of the most object side lens component in thesecond lens group becomes large, and it becomes difficult to correctsuperbly spherical aberration and other various aberrations. Meanwhile,in order to secure the advantageous effect of the variable magnificationoptical system according to the present embodiment more surely, it ispreferable to set the lower limit value of the conditional expression(10) to 0.600. And in order to secure the advantageous effect of thepresent embodiment much more surely, it is preferable to set the lowerlimit value of the conditional expression (10) to 0.650 and morepreferable to 0.700.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the following conditionalexpression (11) is satisfied:

0.300<fF/ft<1.400  (11)

where fF denotes a focal length of the focusing lens group, and ftdenotes a focal length of the variable magnification optical system inthe telephoto end state.

The conditional expression (11) defines a ratio of the focal length ofthe focusing lens group relative to the focal length of the variablemagnification optical system in the tele photo end state. Withsatisfying the conditional expression (11), the variable magnificationoptical system according to the present embodiment can suppressvariations in spherical aberration and in other various aberrations uponfocusing from an infinite distance object to a close distance object,and the variable magnification optical system and the lens barrel may bemade small-sized.

When the value of fF/ft is equal to or exceeds the upper limit value ofthe conditional expression (11) of the variable magnification opticalsystem according to the present embodiment, refractive power of thefocusing lens group becomes small, and it becomes difficult to correctsuperbly variations in various aberrations and, in particular, variationin spherical aberration, upon focusing from an infinite distance objectto a close distance object. Meanwhile, in order to secure theadvantageous effect of the present embodiment more surely, it ispreferable to set the upper limit value of the conditional expression(11) to 1.000. Further, in order to secure the advantageous effect ofthe present embodiment much more surely, it is preferable to set theupper limit value of the conditional expression (11) to 0.900, and morepreferable to 0.850.

On the other hand, when the value of fF/ft in the conditional expression(11) of the variable magnification optical system according to thepresent embodiment, is equal to or falls below the lower limit value,refractive power of the focusing lens group becomes large, and itbecomes difficult to correct variations in various aberrations uponfocusing from an infinite distance object to a close distance objectand, in particular, variation in spherical aberration superbly.Meanwhile, in order to secure the advantageous effect of the presentembodiment more surely, it is preferable to set the lower limit value ofthe conditional expression (11) to 0.500. And in order to secure theadvantageous effect of the present embodiment much more surely, it ispreferable to set the lower limit value of the conditional expression(11) to 0.600, and more preferable to 0.700.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(12) is satisfied:

40.00°<ωw<85.00°  (12)

where ωw denotes a half angle of view of the variable magnificationoptical system in the wide angle end state.

The conditional expression (12) defines the half angle of view of thevariable magnification optical system in the wide angle end state. Withsatisfying the conditional expression (12), the variable magnificationoptical system according to the present embodiment can correct superblyvarious aberrations such as coma aberration, distortion and curvature offield and others, while maintaining large angle of view.

When the value of cow is equal to or exceeds the upper limit value ofthe conditional expression (12) of the variable magnification opticalsystem according to the present embodiment, the angle of view becomestoo large and it becomes difficult to correct superbly variousaberrations, such as, coma aberration, distortion and curvature offield. Meanwhile, in order to secure the advantageous effect of thepresent embodiment more surely, it is preferable to set the upper limitvalue of the conditional expression (12) to 84.00°. Further, in order tosecure the advantageous effect of the present embodiment much moresurely, it is preferable to set the upper limit value of the conditionalexpression (12) to 83.00°, and more preferable to 82.00°.

On the other hand, when the value of cow in the conditional expression(12) of the variable magnification optical system according to thepresent embodiment, is equal to or falls below the lower limit value,the angle of view becomes small and it becomes difficult to correctsuperbly various aberrations. Meanwhile, in order to secure theadvantageous effect of the present embodiment more surely, it ispreferable to set the lower limit value of the conditional expression(12) to 41.00°. Further, in order to secure the advantageous effect ofthe present embodiment much more surely, it is preferable to set thelower limit value of the conditional expression (12) to 42.00°, and morepreferable to 43.00°.

The optical apparatus of the present embodiment is equipped with thevariable magnification optical system having the above describedconfiguration, so it is possible to realize an optical apparatus whichis compatible with a large-sized imaging device in spite that theoptical apparatus is small-sized, and which can correct superbly variousaberrations upon varying magnification as well as upon focusing.

A method for manufacturing a variable magnification optical systemaccording to the present embodiment, is a method for manufacturing avariable magnification optical system which comprises, in order from anobject side, a first lens group having positive refractive power, asecond lens group having negative refractive power, a third lens grouphaving positive refractive power and a rear lens group having positiverefractive power; configuring such that, upon varying a magnificationfrom a wide angle end state to a telephoto end state, a distance betweensaid first lens group and said second lens group is varied, a distancebetween said second lens group and said third lens group is varied, anda distance between said third lens group and said rear lens group isvaried;

configuring such that said rear lens group comprises a focusing lensgroup which is moved upon carrying out focusing from an infinitedistance object to a close distance object; and

configuring such that the following conditional expressions (1) and (2)are satisfied:

−1.00<f3f/f3r<−0.0500  (1)

0.100<BFw/fw<1.00  (2)

where f3f denotes a focal length of a most image plane side negativelens component in said third lens group; f3r denotes a composite focallength of lens components disposed on a side which is closer to theobject than said most image plane side negative lens component in saidthird lens group; BFw denotes aback focus of said variable magnificationoptical system in a wide angle end state; and fw denotes a focal lengthof said variable magnification optical system in the wide angle endstate.

By this method, it is possible to manufacture a variable magnificationoptical system which is compatible with a large-sized imaging device inspite that the optical system is small-sized, and which can correctsuperbly various aberrations upon varying magnification as well as uponfocusing.

Hereinafter, the variable magnification optical systems relating tonumerical examples of the present embodiment will be explained withreference to the accompanying drawings.

First Example

FIGS. 1A, 1B and 1C are, respectively, cross sectional views in a wideangle end state, in an intermediate focal length state and in antelephoto end state, of a variable magnification optical systemaccording to a First Example of the variable magnification opticalsystem of the present embodiment. Arrows below each lens group in FIG.1A show directions of movements of respective lens groups upon varyingmagnification from a wide angle end state to an intermediate focallength state. Arrows below each lens group in FIG. 1B show movementtrajectories of respective lens groups upon varying magnification fromthe intermediate focal length state to a telephoto end state.

The variable magnification optical system according to the presentExample is composed of, in order from an object side along the opticalaxis, a first lens group G1 having positive refractive power, a secondlens group G2 having negative refractive power, an aperture stop S, athird lens group G3 having positive refractive power, and a rear lensgroup GR having positive refractive power.

The first lens group G1 consists of a cemented lens constructed by, inorder from the object side along the optical axis, a negative meniscuslens L11 having a convex surface facing the object side cemented with apositive meniscus lens L12 having a convex surface facing the objectside.

The second lens group G2 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L21 having a convexsurface facing the object side, a double concave negative lens L22, anda positive meniscus lens L23 having a convex surface facing the objectside. The negative meniscus lens L21 is a glass mold type asphericallens whose image plane I side lens surface is aspherical.

The third lens group G3 consists of, in order from the object side alongthe optical axis, a double convex positive lens L31, a cemented lensconstructed by a negative meniscus lens L32 having a convex surfacefacing the object side cemented with a double convex positive lens L33,and a cemented lens constructed by a double concave negative lens L34cemented with a double convex positive lens L35. The double convexpositive lens L31 is a glass mold type aspherical lens whose object sidelens surface is aspherical.

The rear lens group GR is composed of, in order from the object sidealong the optical axis, a fourth lens group G4 having positiverefractive power and a fifth lens group G5 having negative refractivepower.

The fourth lens group G4 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L41 having a concavesurface facing the object side, and a double convex positive lens L42.The double convex positive lens L42 is a glass mold type aspherical lenswhose image plane I side lens surface is aspherical.

The fifth lens group G5 consists of, in order from the object side alongthe optical axis, a positive meniscus lens L51 having a concave surfacefacing the object side and a double concave negative lens L52. Thepositive meniscus lens L51 is a glass mold type aspherical lens whoseimage plane I side lens surface is aspherical.

A filter FL such as a low pass filter is disposed between the fifth lensgroup G5 and the image plane I.

On the image plane I, an imaging device (not shown) composed of CCD,CMOS or the like is disposed.

In the variable magnification optical system according to the presentExample, upon varying magnification from the wide angle end state to thetelephoto end state, all lens groups of the first lens group G1 to thefifth lens group G5 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4,and a distance between the fourth lens group G4 and the fifth lens groupG5, are varied. The aperture stop S is moved in a body with the thirdlens group G3 upon varying magnification from the wide angle end stateto the telephoto end state.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4 toward theobject along the optical axis as a focusing lens group.

Table 1 below shows various values of the variable magnification opticalsystem relating to the present Example.

In [Surface Data], “m” denotes an order of an optical surface countedfrom the object side, “r” denotes a radius of curvature, “d” denotes asurface-to-surface distance, that is, an interval from an n-th surfaceto an (n+1)-th surface, where n is an integer, “nd” denotes refractiveindex for d-line (wavelength λ=587.6 nm) and “νd” denotes an Abbe'snumber for d-line (wavelength λ=587.6 nm). Further, “OP” denotes anobject surface, “Dn” denotes a variable surface-to-surface distance,where n is an integer, “S” denotes an aperture stop, and “I” denotes animage plane. Meanwhile, radius of curvature r=∞ denotes a plane surface,and refractive index of the air nd=1.00000 is omitted. In addition, anaspherical surface is expressed by attaching “*” to the surface number,and in the column of the radius of curvature “r”, a paraxial radius ofcurvature is shown.

In [Various Data], “f” denotes a focal length, “FNO” denotes anF-number, “ω” denotes a half angle of view (unit “°”), “Y” denotes amaximum image height, and “TL” denotes a total length of the variablemagnification optical system according to the present Example, that is,a distance along the optical axis from the first lens surface to theimage plane I. BF denotes a back focus, that is, a distance on theoptical axis from a most image side lens surface to the image plane I,and BF (air converted length) is a value of the distance on the opticalaxis from the most image side lens surface to the image plane I measuredin a state where optical block(s) such as filter(s) is (are) removedfrom on the optical path. Meanwhile, “W” denotes a wide angle end state,“M” denotes an intermediate focal length state, “T” denotes a tele photoend state.

In [Lens Group Data], a starting surface number “ST” and a focal length“f” of each lens group are shown.

In [Aspherical Surface Data], with respect to aspherical surface (s)shown in the [Surface Data], a shape of the aspherical surface isexhibited by the following expression:

X=(h ² /r)/[1+[1−κ(h/r)²]^(1/2)]+A4h ⁴ +A6h ⁶ +A8h ⁸ +A10y ¹⁰

where h denotes a vertical height from the optical axis; X denotes a sagamount which is a distance along the optical axis from the tangent planeat the vertex of the aspherical surface to the aspherical surface at thevertical height h; κ denotes a conical coefficient; A4, A6, A8 and A10each denotes an aspherical surface coefficient; r denotes a radius ofcurvature of a reference sphere, that is, a paraxial radius ofcurvature. Meanwhile, “E-n” denotes “×10^(−n)”, in which “n” is aninteger, and for example “1.234E-05” denotes “1.234×10⁻⁵”. The secondorder aspherical coefficient A2 is 0 and omitted.

In [Variable Distance Data], Dn denotes a surface to surface distancefrom n-th surface to (n+1)-th surface, where n is an integer. Further, Wdenotes a wide-angle end state, M denotes an intermediate focal lengthstate, T denotes a telephoto end state, “Infinite” denotes time on whichan infinite distance object is focused, and “Close” denotes time onwhich a close distance object is focused.

In [Values for Conditional Expressions], values with respect torespective conditional expressions are shown.

The focal length “f”, the radius of curvature “r” and other units on thelength described in Table 1 involve using generally [mm], however, theoptical system acquires the equal optical performance even whenproportionally enlarged or reduced and is not therefore limited to thisunit.

Note that the descriptions of the reference numerals and symbols inTable 1 are the same in the subsequent Examples.

TABLE 1 First Example [Surface Data] m r d nd υd OP ∞  1 73.00000 2.1501.84666 23.8  2 47.49515 8.600 1.75500 52.3  3 417.04330 D3  4 400.000001.800 1.74353 49.5  *5 17.04241 8.087  6 −181.13172 1.350 1.75500 52.3 7 49.98466 2.108  8 37.80684 3.693 2.00069 25.5  9 235.22758 D9  10(S)∞ 1.500 *11 25.88353 4.048 1.55332 71.7  12 −254.63176 0.800  1352.19394 1.000 1.83481 42.7  14 26.38369 3.546 1.61800 63.3  15−150.00000 3.743  16 −33.68615 1.000 1.81600 46.6  17 17.28639 6.4941.59319 67.9  18 −23.04098 D18  19 −22.45485 1.000 1.80100 34.9  20−41.05177 0.103  21 59.92172 6.115 1.59201 67.0 *22 −26.25646 D22  23−40.60645 3.489 1.58913 61.2 *24 −24.00000 5.786  25 −24.36536 1.5001.61800 63.3  26 107.45414 D26  27 ∞ 1.600 1.51680 64.1  28 ∞ D28 I ∞[Various Data] Variable magnification ratio 2.75 W M T f 24.72 46.3167.91 FNo 4.00 4.00 4.00 ω 43.3 24.0 16.7 Y 21.70 21.70 21.70 TL 121.583134.978 151.029 BF 15.558 28.486 36.144 BF(air converted length) 15.01327.941 35.599 [Lens Group Data] Lens Group ST f 1^(st) Lens Group 1125.09 2^(nd) Lens Group 4 −28.96 3^(rd) Lens Group 10 39.65 4^(th) LensGroup 19 56.05 5^(th) Lens Group 23 −51.52 [Aspherical Surface Data]Surface Number: 5 K = 0.00000e+00 A4 = 2.11342e−05 A6 = 4.21453e−08 A8 =−3.77216e−11 A10 = 4.44697e−13 Surface Number: 11 K = 1.00000e+00 A4 =−5.01541e−06 A6 = 1.10914e−09 A8 = 4.72876e−11 A10 = −3.55280e−13Surface Number: 22 K = 1.00000e+00 A4 = 1.52181e−05 A6 = −2.09730e−08 A8= −1.77284e−11 A10 = −1.36838e−13 Surface Number: 24 K = 1.00000e+00 A4= 3. 09258e−06 A6 = 3.56902e−08 A8 = −3.36788e−11 A10 = 3.80333e−13[Variable Distance Data] W M T W M T Infinite Infinite Infinite CloseClose Close D3 1.600 17.195 31.254 1.600 17.195 31.254 D9 23.690 8.5622.895 23.690 8.562 2.895 D18 4.579 8.446 10.823 2.148 3.205 2.313 D228.245 4.378 2.000 10.675 9.619 10.510 D26 13.858 26.785 34.444 13.85826.785 34.444 D28 0.100 0.101 0.101 0.100 0.101 0.101 [Values forConditional Expressions] (1) f3f/f3r = −0.2127 (2) BFw/fw = 0.6901 (3)f1/fw = 5.0602 (4) βFw = 0.5234 (5) f5/f3 = −1.2993 (6) f1/f1Rw = 5.7747(7) nd3fp = 1.5533 (8) υd3p = 71.6835 (9) 1/βRw = 0.7853 (10) f2fn/f2 =0.8285 (11) fF/ft = 0.8254 (12) ωw = 43.3420°

FIG. 2A, FIG. 2B and FIG. 2C are graphs showing various aberrations uponfocusing on an infinite distance object, respectively, in the wide angleend state, in the intermediate focal length state and in the telephotoend state, of the variable magnification optical system according to theFirst Example.

FIG. 3A, FIG. 3B and FIG. 3C are graphs showing various aberrations uponfocusing on a close distance object, respectively, in the wide angle endstate, in the intermediate focal length state and in the telephoto endstate, of the variable magnification optical system according to theFirst Example.

In the respective graphs showing aberrations, “FNO” denotes an F-number,“NA” denotes a numerical aperture, and “A” denotes an incident angle oflight rays, that is, a half angle of view (unit “°”), and “HO” denotesan object height (unit: mm). In detail, in graphs showing sphericalaberrations, the value of F-number FNO or numerical aperture NAcorresponding to the maximum aperture is shown. In graphs showingastigmatism and distortions, the maximum values of the half angle ofview or of the object height are shown respectively, and in graphsshowing coma aberration, each half angle of view or each object heightis shown. “d” denotes abberatino for d-line (wavelength λ=587.6 nm), “g”denotes abberatino for g-line (wavelength λ=435.8 nm), and graphs with“g” or “d” being not attached, show aberration for d-line. In graphsshowing astigmatism, a solid line indicates a sagittal image plane, anda broken line indicates a meridional image plane. In graphs showing comaaberration, coma aberration in each half angle of view or each objectheight, that is, transverse aberration is shown. Meanwhile, in graphsshowing various aberrations in the respective Examples as describedbelow, the same symbols as in the present Example are employed.

As is apparent from the above-mentioned graphs showing aberrations, itis understood that the variable magnification optical system relating tothe present Example can correct superbly various aberrations over thewide angle end state to the telephoto end state and has excellentimaging performance, and further has excellent imaging performance evenupon focusing on a close distance object.

Second Example

FIG. 4A, FIG. 4B and FIG. 4C are, respectively, cross sectional views ina wide angle end state, in an intermediate focal length state and in atelephoto end state, of a variable magnification optical systemaccording to a Second Example of the variable magnification opticalsystem of the present embodiment. Arrows below each lens group in FIG.4A show directions of movements of respective lens groups upon varyingmagnification from the wide angle end state to the intermediate focallength state. Arrows below each lens group in FIG. 4B show movementtrajectories of respective lens groups upon varying magnification fromthe intermediate focal length state to the telephoto end state.

The variable magnification optical system according to the presentExample is composed of, in order from an object side along the opticalaxis, a first lens group G1 having positive refractive power, a secondlens group G2 having negative refractive power, an aperture stop S, athird lens group G3 having positive refractive power, and a rear lensgroup GR having positive refractive power.

The first lens group G1 consists of a cemented lens constructed by, inorder from the object side along the optical axis, a negative meniscuslens L11 having a convex surface facing the object side cemented with apositive meniscus lens L12 having a convex surface facing the objectside.

The second lens group G2 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L21 having a convexsurface facing the object side, a double concave negative lens L22, anda positive meniscus lens L23 having a convex surface facing the objectside. The negative meniscus lens L21 is a glass mold type asphericallens whose image plane I side lens surface is aspherical.

The third lens group G3 consists of, in order from the object side alongthe optical axis, a double convex positive lens L31, a cemented lensconstructed by a negative meniscus lens L32 having a convex surfacefacing the object side cemented with a double convex positive lens L33,and a cemented lens constructed by a double concave negative lens L34cemented with a double convex positive lens L35. The double convexpositive lens L31 is a glass mold type aspherical lens whose object sidelens surface is aspherical.

The rear lens group GR is composed of, in order from the object sidealong the optical axis, a fourth lens group G4 having positiverefractive power and a fifth lens group G5 having negative refractivepower.

The fourth lens group G4 consists of, in order from the object side, anegative meniscus lens L41 having a concave surface facing the objectside, and a double convex positive lens L42. The double convex positivelens L42 is a glass mold type aspherical lens whose image plane I sidelens surface is aspherical.

The fifth lens group G5 consists of, in order from the object side alongthe optical axis, a positive meniscus lens L51 having a concave surfacefacing the object side and a double concave negative lens L52. Thepositive meniscus lens L51 is a glass mold type aspherical lens whoseimage plane I side lens surface is aspherical.

A filter FL such as a low pass filter is disposed between the fifth lensgroup G5 and the image plane I.

On the image plane I, an imaging device (not shown) composed of CCD,CMOS or the like is disposed.

In the variable magnification optical system according to the presentExample, upon varying magnification from the wide angle end state to thetelephoto end state, all lens groups of the first lens group G1 to thefifth lens group G5 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4,and a distance between the fourth lens group G4 and the fifth lens groupG5, are varied. The aperture stop S is moved in a body with the thirdlens group G3 upon varying magnification from the wide angle end stateto the telephoto end state.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4 toward theobject along the optical axis as a focusing lens group.

Table 2 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 2 Second Example [Surface Data] m r d nd υd OP ∞  1 71.32483 2.1501.84666 23.8  2 47.40907 8.400 1.75500 52.3  3 322.63295 D3  4 400.000001.800 1.74353 49.5  *5 16.36859 9.475  6 −167.05753 2.029 1.75500 52.3 7 52.89355 0.797  8 36.08835 4.010 2.00069 25.5  9 256.44936 D9  10(S)∞ 1.500 *11 25.91417 3.857 1.55332 71.7  12 −275.22572 1.078  1351.71743 1.000 1.83481 42.7  14 21.38295 4.402 1.61800 63.3  15−80.10599 3.539  16 −29.70942 1.000 1.81600 46.6  17 18.35723 5.5821.59349 67.0  18 −21.31475 D18  19 −21.98830 1.000 1.74950 35.2  20−53.12352 0.100  21 62.90338 5.816 1.62263 58.2 *22 −25.22856 D22  23−35.90246 3.521 1.62263 58.2 *24 −23.00000 6.177  25 −23.30716 1.5001.61800 63.3  26 150.39447 D26  27 ∞ 1.600 1.51680 64.1  28 ∞ D28 I ∞[Various Data] Variable magnification ratio 2.75 W M T f 24.72 46.3167.90 FNo 4.00 4.00 4.00 ω 43.6 24.3 16.8 Y 21.70 21.70 21.70 TL 122.013134.611 152.248 BF 15.085 29.244 35.661 BF(air converted length) 14.54028.699 35.116 [Lens Group Data] Lens Group ST f 1^(st) Lens Group 1128.74 2^(nd) Lens Group 4 −28.81 3^(rd) Lens Group 10 38.09 4^(th) LensGroup 19 60.73 5^(th) Lens Group 23 −52.48 [Aspherical Surface Data]Surface Number: 5 K = 0.00000e+00 A4 = 2.31089e−05 A6 = 3.91931e−08 A8 =8.80919e−12 A10 = 3.83889e−13 Surface Number: 11 K = 1.00000e+00 A4 =−6.11034e−06 A6 = 4.65530e−09 A8 = −7.97458e−11 A10 = 3.48297e−13Surface Number: 22 K = 1.00000e+00 A4 = 1.49147e−05 A6 = −1.52664e−08 A8= −4.38703e−11 A10 = −3.36461e−14 Surface Number: 24 K = 1.00000e+00 A4= 3.38657e−06 A6 = 2.78770e−08 A8 = 3.43065e−11 A10 = 1.67177e−13[Variable Distance Data] W M T W M T Infinite Infinite Infinite CloseClose Close D3 1.607 15.176 31.798 1.607 15.176 31.798 D9 23.402 8.2722.870 23.402 8.272 2.870 D18 4.665 9.193 11.184 2.019 3.622 2.045 D228.519 3.992 2.000 11.165 9.562 11.139 D26 13.385 27.544 33.962 13.38527.544 33.962 D28 0.100 0.099 0.099 0.099 0.099 0.099 [Values forConditional Expressions] (1) f3f/f3r = −0.2058 (2) BFw/fw = 0.6709 (3)f1/fw = 5.2079 (4) βFw = 0.5717 (5) f5/f3 = −1.3777 (6) f1/f1Rw = 5.9279(7) nd3fp = 1.5533 (8) υd3p = 71.6835 (9) 1/βRw = 0.7923 (10) f2fn/f2 =0.7983 (11) fF/ft = 0.8944 (12) ωw = 43.6046°

FIG. 5A, FIG. 5B and FIG. 5C are graphs showing various aberrations uponfocusing on an infinite distance object, respectively, in the wide angleend state, in the intermediate focal length state and in the telephotoend state, of the variable magnification optical system according to theSecond Example.

FIG. 6A, FIG. 6B and FIG. 6C are graphs showing various aberrations uponfocusing on a close distance object, respectively, in the wide angle endstate, in the intermediate focal length state and in the telephoto endstate, of the variable magnification optical system according to theSecond Example.

As is apparent from the above-mentioned graphs showing aberrations, itis understood that the variable magnification optical system relating tothe present Example can correct superbly various aberrations over thewide angle end state to the telephoto end state and has excellentimaging performance, and further has excellent imaging performance evenupon focusing on a close distance object.

Third Example

FIG. 7A, FIG. 7B and FIG. 7C are, respectively, cross sectional views ina wide angle end state, in an intermediate focal length state and in atelephoto end state, of a variable magnification optical systemaccording to a Third Example of the variable magnification opticalsystem of the present embodiment. Arrows below each lens group in FIG.7A show directions of movements of respective lens groups upon varyingmagnification from a wide angle end state to an intermediate focallength state. Arrows below each lens group in FIG. 7B show movementtrajectories of respective lens groups upon varying magnification fromthe intermediate focal length state to a telephoto end state.

The variable magnification optical system according to the presentExample is composed of, in order from an object side along the opticalaxis, a first lens group G1 having positive refractive power, a secondlens group G2 having negative refractive power, an aperture stop S, athird lens group G3 having positive refractive power, and a rear lensgroup GR having positive refractive power.

The first lens group G1 consists of a cemented lens constructed by, inorder from the object side along the optical axis, a negative meniscuslens L11 having a convex surface facing the object side cemented with apositive meniscus lens L12 having a convex surface facing the objectside.

The second lens group G2 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L21 having a convexsurface facing the object side, a double concave negative lens L22, anda positive meniscus lens L23 having a convex surface facing the objectside. The negative meniscus lens L21 is a glass mold type asphericallens whose image plane I side lens surface is aspherical.

The third lens group G3 consists of, in order from the object side alongthe optical axis, a positive meniscus lens L31 having a convex surfacefacing the object side, a cemented lens constructed by a negativemeniscus lens L32 having a convex surface facing the object sidecemented with a double convex positive lens L33, and a cemented lensconstructed by a double concave negative lens L34 cemented with a doubleconvex positive lens L35. The positive meniscus lens L31 is a glass moldtype aspherical lens whose object side lens surface is aspherical.

The rear lens group GR is composed of, in order from the object sidealong the optical axis, a fourth lens group G4 having positiverefractive power and a fifth lens group G5 having negative refractivepower.

The fourth lens group G4 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L41 having a concavesurface facing the object side, and a double convex positive lens L42.The double convex positive lens L42 is a glass mold type aspherical lenswhose image plane I side lens surface is aspherical.

The fifth lens group G5 consists of, in order from the object side alongthe optical axis, a positive meniscus lens L51 having a concave surfacefacing the object side and a double concave negative lens L52. Thepositive meniscus lens L51 is a glass mold type aspherical lens whoseimage plane I side lens surface is aspherical.

A filter FL such as a low pass filter is disposed between the fifth lensgroup G5 and the image plane I. On the image plane I, an imaging device(not shown) composed of CCD, CMOS or the like is disposed.

In the variable magnification optical system according to the presentExample, upon varying magnification from the wide angle end state to thetelephoto end state, all lens groups of the first lens group G1 to thefifth lens group G5 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4,and a distance between the fourth lens group G4 and the fifth lens groupG5, are varied. The aperture stop S is moved in a body with the thirdlens group G3 upon varying magnification from the wide angle end stateto the telephoto end state.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4 toward theobject along the optical axis as a focusing lens group.

Table 3 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 3 Third Example [Surface Data] m r d nd νd OP ∞  1 77.74447 2.1501.84666 23.8  2 53.55851 8.020 1.72916 54.6  3 478.39025 D3   41000.00000 2.000 1.74250 49.4 *5 17.13499 9.008  6 −103.78967 1.5001.75500 52.3  7 80.88445 0.942  8 41.82797 3.959 2.00069 25.5  9874.65992 D9  10(S) ∞ 1.500 *11  25.63046 3.669 1.55332 71.7 12649.10845 0.500 13 43.22955 1.000 1.83481 42.7 14 18.28418 4.715 1.6180063.3 15 −90.27190 4.286 16 −32.75074 1.000 1.81600 46.6 17 18.815335.331 1.59349 67.0 18 −22.38426 D18 19 −20.95545 1.000 1.80610 33.3 20−38.43736 0.450 21 70.13258 6.000 1.62263 58.2 *22  −25.20560 D22 23−28.47777 3.307 1.69350 53.3 *24  −21.27208 6.193 25 −24.27627 1.5001.61881 63.9 26 106.34326 D26 27 ∞ 1.600 1.51680 64.1 28 ∞ D28 I ∞[Various Data] Variable magnification ratio 2.75 W M T f 24.72 46.3167.90 FNo 4.00 4.28 4.00 ω 43.9 24.1 16.6 Y 21.70 21.70 21.70 TL 121.939132.931 151.948 BF 14.546 28.656 35.001 BF (air converted 14.000 28.11134.456 length) [Lens Group Data] Lens Group ST f 1^(st) Lens Group  1137.34 2^(nd) Lens Group  4 −31.18 3^(rd) Lens Group 10 38.77 4^(th)Lens Group 19 54.86 5^(th) Lens Group 23 −47.21 [Aspherical SurfaceData] Surface Number: 5 K = 0.00000e+00 A4 = 2.00686e−05 A6 =2.97810e−08 A8 = 2.98043e−11 A10 = 1.72509e−13 Surface Number: 11 K =1.00000e+00 A4 = −5.31955e−06 A6 = 1.45892e−09 A8 = 2.19477e−11 A10 =−2.48946e−13 Surface Number: 22 K = 1.00000e+00 A4 = 1.44228e−05 A6 =−1.30721e−08 A8 = 5.35466e−12 A10 = −2.19209e−13 Surface Number: 24 K =1.00000e+00 A4 = 5.35295e−06 A6 = 2.89950e−08 A8 = −2.95842e−11 A10 =3.75280e−13 [Variable Distance Data] W M T W M T Infinite InfiniteInfinite Close Close Close D3  1.704 15.094 33.353 1.704 15.094 33.353D9  24.986 8.476 2.890 24.986 8.476 2.890 D18 4.613 8.792 10.677 2.1833.795 2.527 D22 8.064 3.886 2.000 10.494 8.882 10.150 D26 12.846 26.95833.303 12.846 26.958 33.303 D28 0.100 0.099 0.098 0.099 0.098 0.098[Values for Conditional Expressions]  (1) f3f/f3r = −0.2001  (2) BFw/fw= 0.6491  (3) f1/fw = 5.5559  (4) βFw = 0.5546  (5) f5/f3 = −1.2178  (6)fl/f1Rw = 6.2478  (7) nd3fp = 1.5533  (8) νd3p = 71.6835  (9) 1/βRw =0.7706 (10) f2fn/f2 = 0.7537 (11) fF/ft = 0.8080 (12) ωw = 43.9044°

FIG. 8A, FIG. 8B and FIG. 8C are graphs showing various aberrations uponfocusing on an infinite distance object, respectively, in the wide angleend state, in the intermediate focal length state and in the telephotoend state, of the variable magnification optical system according to theThird Example.

FIG. 9A, FIG. 9B and FIG. 9C are graphs showing various aberrations uponfocusing on a close distance object, respectively, in the wide angle endstate, in the intermediate focal length state and in the telephoto endstate, of the variable magnification optical system according to theThird Example.

As is apparent from the above-mentioned graphs showing aberrations, itis understood that the variable magnification optical system relating tothe present Example can correct superbly various aberrations over thewide angle end state to the telephoto end state and has excellentperformance, and further has excellent imaging performance even uponfocusing on a close distance object.

Fourth Example

FIG. 10A, FIG. 10B and FIG. 10C are, respectively, cross sectional viewsin a wide angle end state, in an intermediate focal length state and ina telephoto end state, of a variable magnification optical systemaccording to a Fourth Example of the variable magnification opticalsystem of the present embodiment. Arrows below each lens group in FIG.10A show directions of movements of respective lens groups upon varyingmagnification from a wide angle end state to an intermediate focallength state. Arrows below each lens group in FIG. 10B show movementtrajectories of respective lens groups upon varying magnification fromthe intermediate focal length state to a telephoto end state.

The variable magnification optical system according to the presentExample is composed of, in order from an object side along the opticalaxis, a first lens group G1 having positive refractive power, a secondlens group G2 having negative refractive power, an aperture stop S, athird lens group G3 having positive refractive power, and a rear lensgroup GR having positive refractive power.

The first lens group G1 consists of a cemented lens constructed by, inorder from the object side along the optical axis, a negative meniscuslens L11 having a convex surface facing the object side cemented with apositive meniscus lens L12 having a convex surface facing the objectside.

The second lens group G2 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L21 having a convexsurface facing the object side, a double concave negative lens L22, anda positive meniscus lens L23 having a convex surface facing the objectside. The negative meniscus lens L21 is a glass mold type asphericallens whose image plane I side lens surface is aspherical.

The third lens group G3 consists of, in order from the object side alongthe optical axis, a positive meniscus lens L31 having a convex surfacefacing the object side, a cemented lens constructed by a negativemeniscus lens L32 having a convex surface facing the object sidecemented with a double convex positive lens L33, and a cemented lensconstructed by a double concave negative lens L34 cemented with a doubleconvex positive lens L35. The positive meniscus lens L31 is a glass moldtype aspherical lens whose object side lens surface is aspherical.

The rear lens group GR is composed of, in order from the object sidealong the optical axis, a fourth lens group G4 having positiverefractive power and a fifth lens group G5 having negative refractivepower.

The fourth lens group G4 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L41 having a concavesurface facing the object side, and a double convex positive lens L42.The double convex positive lens L42 is a glass mold type aspherical lenswhose image plane I side lens surface is aspherical.

The fifth lens group G5 consists of, in order from the object side, apositive meniscus lens L51 having a concave surface facing the objectside and a double concave negative lens L52. The positive meniscus lensL51 is a glass mold type aspherical lens whose image plane I side lenssurface is aspherical.

A filter FL such as a low pass filter is disposed between the fifth lensgroup G5 and the image plane I.

On the image plane I, an imaging device (not shown) composed of CCD,CMOS or the like is disposed.

In the variable magnification optical system according to the presentExample, upon varying magnification from the wide angle end state to thetelephoto end state, all lens groups of the first lens group G1 to thefifth lens group G5 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4,and a distance between the fourth lens group G4 and the fifth lens groupG5, are varied. The aperture stop S is moved in a body with the thirdlens group G3 upon varying magnification from the wide angle end stateto the telephoto end state.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4 toward theobject along the optical axis as a focusing lens group.

Table 4 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 4 Fourth Example [Surface Data] m r d nd νd OP ∞  1 76.69882 2.1501.84666 23.8  2 49.37863 8.183 1.75500 52.3  3 439.48582 D3   41000.00000 2.000 1.74250 49.4 *5 17.13499 9.947  6 −92.86562 1.5001.75500 52.3  7 89.43926 1.284  8 45.22218 3.631 2.00069 25.5  91279.93050 D9  10(S) ∞ 1.500 *11  25.91677 3.597 1.55332 71.7 12261.64746 0.300 13 38.95443 1.000 1.83481 42.7 14 23.18065 4.122 1.6180063.3 15 −155.71305 4.035 16 −65.68195 1.000 1.83481 42.7 17 15.759525.135 1.61800 63.3 18 −32.57355 D18 19 −20.56363 2.000 1.80100 34.9 20−34.41474 1.000 21 89.46436 6.000 1.59201 67.0 *22  −24.96683 D22 23−34.33374 3.425 1.55332 71.7 *24  −23.28316 4.520 25 −24.47581 1.5001.61881 63.9 26 132.00709 D26 27 ∞ 1.500 1.51680 64.1 28 ∞ D28 I ∞[Various Data] Variable magnification ratio 2.75 W M T f 24.72 46.3167.90 FNo 4.00 4.18 4.00 ω 43.6 23.8 16.5 Y 21.70 21.70 21.70 TL 121.051133.285 149.815 BF 14.060 26.434 33.679 BF(air converted 13.549 25.92333.168 length) [Lens Group Data] Lens Group ST f 1^(st) Lens Group  1131.85 2^(nd) Lens Group  4 −29.95 3^(rd) Lens Group 10 35.73 4^(th)Lens Group 19 55.25 5^(th) Lens Group 23 −46.59 [Aspherical SurfaceData] Surface Number: 5 K = 0.00000e+00 A4 = 1.93492e−05 A6 =2.97056e−08 A8 = 3.40451e−11 A10 = 1.36704e−13 Surface Number: 11 K =1.00000e+00 A4 = −5.53738e−06 A6 = 5.67727e−10 A8 = 5.02317e−11 A10 =−4.30689e−13 Surface Number: 22 K = 1.00000e+00 A4 = 1.49131e−05 A6 =−1.16787e−08 A8 = 1.79818e−12 A10 = −2.00447e−13 Surface Number: 24 K =1.00000e+00 A4 = 3.34976e−06 A6 = 2.85281e−08 A8 = −3.37056e−11 A10 =3.81301e−13 [Variable Distance Data] W M T W M T Infinite InfiniteInfinite Close Close Close D3  1.800 17.426 32.352 1.800 17.426 32.352D9  23.692 7.926 2.285 23.692 7.926 2.285 D18 5.643 9.324 11.669 2.9873.852 2.996 D22 8.025 4.345 2.000 10.681 9.817 10.673 D26 12.460 24.83432.078 12.460 24.834 32.078 D28 0.100 0.101 0.101 0.100 0.101 0.101[Values for Conditional Expressions]  (1) f3f/f3r = −0.1708  (2) BFw/fw= 0.6294  (3) f1/fw = 5.3337  (4) βFw = 0.6214  (5) f5/f3 = −1.3040  (6)f1/f1Rw = 6.0287  (7) nd3fp = 1.5533  (8) νd3p = 71.6835  (9) 1/βRw =0.7672 (10) f2fn/f2 = 0.7846 (11) fF/ft = 0.8135 (12) ωw = 43.5536°

FIG. 11A, FIG. 11B and FIG. 11C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Fourth Example.

FIG. 12A, FIG. 12B and FIG. 12C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Fourth Example.

As is apparent from the above-mentioned graphs showing aberrations, itis understood that the variable magnification optical system relating tothe present Example can correct superbly various aberrations over thewide angle end state to the telephoto end state and has excellentimaging performance, and further has excellent imaging performance evenupon focusing on a close distance object.

Fifth Example

FIG. 13A, FIG. 13B and FIG. 13C are, respectively, cross sectional viewsin a wide angle end state, in an intermediate focal length state and ina telephoto end state, of a variable magnification optical systemaccording to a Fifth Example of the variable magnification opticalsystem of the present embodiment. Arrows below each lens group in FIG.13A show directions of movements of respective lens groups upon varyingmagnification from a wide angle end state to an intermediate focallength state. Arrows below each lens group in FIG. 13B show movementtrajectories of respective lens groups upon varying magnification fromthe intermediate focal length state to a telephoto end state.

The variable magnification optical system according to the presentExample is composed of, in order from an object side along the opticalaxis, a first lens group G1 having positive refractive power, a secondlens group G2 having negative refractive power, an aperture stop S, athird lens group G3 having positive refractive power, and a rear lensgroup GR having positive refractive power.

The first lens group G1 consists of a cemented lens constructed by, inorder from the object side along the optical axis, a negative meniscuslens L11 having a convex surface facing the object side cemented with apositive meniscus lens L12 having a convex surface facing the objectside.

The second lens group G2 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L21 having a convexsurface facing the object side, a double concave negative lens L22, anda positive meniscus lens L23 having a convex surface facing the objectside. The negative meniscus lens L21 is a glass mold type asphericallens whose object side lens surface and image plane I side lens surfaceare aspherical.

The third lens group G3 consists of, in order from the object side alongthe optical axis, a positive meniscus lens L31 having a convex surfacefacing the object side, a cemented lens constructed by a double convexpositive lens L32 cemented with a negative meniscus lens L33 having aconcave surface facing the object side and a cemented lens constructedby a double concave negative lens L34 cemented with a double convexpositive lens L35. The positive meniscus lens L31 is a glass mold typeaspherical lens whose object side lens surface is aspherical.

The rear lens group GR is composed of, in order from the object sidealong the optical axis, a fourth lens group G4 having positiverefractive power and a fifth lens group G5 having negative refractivepower.

The fourth lens group G4 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L41 having a concavesurface facing the object side, and a double convex positive lens L42.The double convex positive lens L42 is a glass mold type aspherical lenswhose image plane I side lens surface is aspherical.

The fifth lens group G5 consists of, in order from the object side alongthe optical axis, a double concave negative lens L51 and a positivemeniscus lens L52 having a convex surface facing the object side.

A filter FL such as a low pass filter is disposed between the fifth lensgroup G5 and the image plane I.

On the image plane I, an imaging device (not shown) composed of CCD,CMOS or the like is disposed.

In the variable magnification optical system according to the presentExample, upon varying magnification from the wide angle end state to thetelephoto end state, all lens groups of the first lens group G1 to thefifth lens group G5 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4,and a distance between the fourth lens group G4 and the fifth lens groupG5, are varied. The aperture stop S is moved in a body with the thirdlens group G3 upon varying magnification from the wide angle end stateto the telephoto end state.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4 toward theobject along the optical axis as a focusing lens group.

Table 5 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 5 Fifth Example [Surface Data] m r d nd νd OP ∞  1 78.28661 2.2001.94595 18.0  2 55.12139 7.465 1.83481 42.7  3 416.58751 D3  *4600.00000 2.000 1.74330 49.3 *5 14.79065 9.268  6 −80.00000 1.5001.49782 82.6  7 112.11004 0.150  8 35.97822 3.589 2.00069 25.5  9115.26124 D9  10(S) ∞ 1.500 *11  22.34807 3.756 1.61881 63.9 12215.30357 4.534 13 116.19602 4.736 1.61800 63.3 14 −16.99559 1.0001.61266 44.5 15 −42.70583 0.150 16 −3080.10830 1.000 1.83481 42.7 1714.42589 4.664 1.49782 82.6 18 −73.51276 D18 19 −32.33307 1.000 1.8010034.9 20 −94.44385 0.415 21 34.51492 5.500 1.69350 53.2 *22  −39.28206D22 23 −146.73735 1.500 1.59319 67.9 24 27.39699 2.426 25 58.23961 2.5941.69895 30.1 26 100.00000 D26 27 ∞ 1.500 1.51680 64.1 28 ∞ D28 I ∞[Various Data] Variable magnification ratio 2.75 W M T f 24.71 46.3067.86 FNo 4.00 4.16 4.00 ω 43.3 23.8 16.5 Y 21.70 21.70 21.70 TL 117.744130.814 147.913 BF 19.640 33.380 41.487 BF(air converted 19.129 32.86940.976 length) [Lens Group Data] Lens Group ST f 1^(st) Lens Group  1121.95 2^(nd) Lens Group  4 −27.81 3^(rd) Lens Group 10 36.02 4^(th)Lens Group 19 45.26 5^(th) Lens Group 23 −48.61 [Aspherical SurfaceData] Surface Number: 4 K = 1.00000e+00 A4 = 1.94041e−06 A6 =−1.27348e−08 A8 = 2.13014e−11 A10 = −1.37676e−14 Surface Number: 5 K =0.00000e+00 A4 = 2.59781e−05 A6 = 6.01951e−08 A8 = −1.23842e−10 A10 =2.09998e−13 Surface Number: 11 K = 1.00000e+00 A4 = −1.43227e−05 A6 =1.69157e−08 A8 = −3.97283e−10 A10 = 1.27743e−12 Surface Number: 22 K =1.00000e+00 A4 = 1.66914e−05 A6 = −1.21729e−08 A8 = −1.24851e−12 A10 =9.57183e−15 [Variable Distance Data] W M T W M T Infinite InfiniteInfinite Close Close Close D3  2.000 16.993 31.289 2.000 16.993 31.289D9  24.595 8.932 3.628 24.595 8.932 3.628 D18 4.555 7.160 9.062 2.8113.351 2.811 D22 6.007 3.402 1.500 7.751 7.211 7.751 D26 18.040 31.78139.888 18.040 31.781 39.888 D28 0.100 0.100 0.100 0.100 0.099 0.100[Values for Conditional Expressions]  (1) f3f/f3r = −0.4100  (2) BFw/fw= 0.8998  (3) f1/fw = 4.9349  (4) βFw = 0.5108  (5) f5/f3 = −1.3496  (6)f1/f1Rw = 5.6533  (7) nd3fp = 1.6188  (8) νd3p = 63.8544  (9) 1/βRw =0.6758 (10) f2fn/f2 = 0.7346 (11) fF/ft = 0.6668 (12) ωw = 43.2711°

FIG. 14A, FIG. 14B and FIG. 14C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Fifth Example.

FIG. 15A, FIG. 15B and FIG. 15C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Fifth Example.

As is apparent from the above-mentioned graphs showing aberrations, itis understood that the variable magnification optical system relating tothe present Example can correct superbly various aberrations over thewide angle end state to the telephoto end state and has excellentimaging performance, and further has excellent imaging performance evenupon focusing on a close distance object.

Sixth Example

FIG. 16A, FIG. 16B and FIG. 16C are, respectively, cross sectional viewsin a wide angle end state, in an intermediate focal length end state andin a telephoto end state, of a variable magnification optical systemaccording to a Sixth Example of the variable magnification opticalsystem of the present embodiment. Arrows below each lens group in FIG.16A show directions of movements of respective lens groups upon varyingmagnification from a wide angle end state to an intermediate focallength state. Arrows below each lens group in FIG. 16B show movementtrajectories of respective lens groups upon varying magnification fromthe intermediate focal length state to a telephoto end state.

The variable magnification optical system according to the presentExample is composed of, in order from an object side along the opticalaxis, a first lens group G1 having positive refractive power, a secondlens group G2 having negative refractive power, an aperture stop S, athird lens group G3 having positive refractive power, and a rear lensgroup GR having positive refractive power.

The first lens group G1 consists of a cemented lens constructed by, inorder from the object side along the optical axis, a negative meniscuslens L11 having a convex surface facing the object side cemented with apositive meniscus lens L12 having a convex surface facing the objectside.

The second lens group G2 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L21 having a convexsurface facing the object side, a double concave negative lens L22, anda positive meniscus lens L23 having a convex surface facing the objectside. The negative meniscus lens L21 is a glass mold type asphericallens whose image plane I side lens surface is aspherical.

The third lens group G3 consists of, in order from the object side alongthe optical axis, a double convex positive lens L31, a cemented lensconstructed by a positive meniscus lens L32 having a concave surfacefacing the object side cemented with a negative meniscus lens L33 havinga concave surface facing the object side, and a cemented lensconstructed by a negative meniscus lens L34 having a convex surfacefacing the object side cemented with a positive meniscus lens L35 havinga convex surface facing the object side. The double convex positive lensL31 is a glass mold type aspherical lens whose object side lens surfaceis aspherical.

The rear lens group GR is composed of, in order from the object sidealong the optical axis, a fourth lens group G4 having positiverefractive power and a fifth lens group G5 having negative refractivepower.

The fourth lens group G4 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L41 having a concavesurface facing the object side, and a positive meniscus lens L42 havinga concave surface facing the object side. The negative meniscus lens L41is a glass mold type aspherical lens whose object side lens surface isaspherical. The positive meniscus lens L42 is a glass mold typeaspherical lens whose image plane I side lens surface is aspherical.

The fifth lens group G5 consists of, in order from the object side alongthe optical axis, a positive meniscus lens L51 having concave surfacefacing the object side and a double concave negative lens L52.

A filter FL such as a low pass filter is disposed between the fifth lensgroup G5 and the image plane I.

On the image plane I, an imaging device (not shown) composed of CCD,CMOS or the like is disposed.

In the variable magnification optical system according to the presentExample, upon varying magnification from the wide angle end state to thetelephoto end state, all lens groups of the first lens group G1 to thefifth lens group G5 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4,and a distance between the fourth lens group G4 and the fifth lens groupG5, are varied. The aperture stop S is moved in a body with the thirdlens group G3 upon varying magnification from the wide angle end stateto the telephoto end state.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4 toward theobject along the optical axis as a focusing lens group.

Table 6 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 6 Sixth Example [Surface Data] m r d nd νd OP ∞  1 60.32635 2.0391.80809 22.7  2 41.97920 8.268 1.75500 52.3  3 207.34902 D3   41000.00000 2.000 1.82886 42.3 *5 15.73567 8.461  6 −59.96573 1.5001.49782 82.6  7 49.78382 0.150  8 35.18437 4.075 1.98917 26.2  91619.58040 D9  10(S) ∞ 1.500 *11  25.50000 4.170 1.55332 71.7 12−65.45591 3.367 13 −32.91804 3.671 1.83645 42.6 14 −14.77178 1.5001.94754 27.1 15 −26.35178 0.150 16 26.26299 1.500 1.99662 26.6 1713.56251 3.695 1.64836 33.2 18 37.92217 D18 *19  −45.13942 1.500 1.5831359.4 20 −55.10622 4.314 21 −45.22291 5.000 1.55332 71.7 *22  −17.65257D22 23 −60.30075 8.069 1.65648 32.5 24 −15.50000 1.500 1.75698 36.7 25290.03399 D25 26 ∞ 1.500 1.51680 64.1 27 ∞ D27 I ∞ [Various Data]Variable magnification ratio 2.75 W M T f 24.72 46.31 67.90 FNo 4.004.09 4.00 ω 44.7 24.0 16.7 Y 21.70 21.70 21.70 TL 116.526 128.486142.973 BF 14.627 25.478 33.218 BF (air converted 14.116 24.967 32.707length) [Lens Group Data] Lens Group ST f 1^(st) Lens Group  1 114.002^(nd) Lens Group  4 −26.90 3^(rd) Lens Group 10 31.86 4^(th) Lens Group19 53.18 5^(th) Lens Group 23 −48.77 [Aspherical Surface Data] SurfaceNumber: 5 K = 0.00000e+00 A4 = 2.28397e−05 A6 = 5.52091e−08 A8 =−3.85159e−11 A10 = 3.96575e−13 Surface Number: 11 K = 1.00000e+00 A4 =−1.02420e−05 A6 = −5.12185e−09 A8 = −2.80701e−11 A10 = −2.18997e−13Surface Number: 19 K = 1.00000e+00 A4 = −3.49441e−05 A6 = −2.07361e−07A8 = 1.87328e−09 A10 = −1.70790e−11 Surface Number: 22 K = 1.00000e+00A4 = 7.10600e−06 A6 = −6.76172e−08 A8 = 4.93526e−10 A10 = −2.53168e−12[Variable Distance Data] W M T W M T Infinite Infinite Infinite CloseClose Close D3  2.000 17.776 29.427 2.000 17.776 29.427 D9  21.834 7.1672.262 21.834 7.167 2.262 D18 4.820 7.522 10.636 2.245 2.026 1.830 D226.816 4.114 1.000 9.392 9.610 9.806 D25 13.027 23.878 31.619 13.02723.878 31.619 D27 0.100 0.100 0.100 0.100 0.100 0.100 [Values forConditional Expressions]  (1) f3f/f3r = −0.0982  (2) BFw/fw = 0.6524 (3) f1/fw = 4.6115  (4) βFw = 0.6567  (5) f5/f3 = −1.5310  (6) f1/f1Rw= 5.3365  (7) nd3fp = 1.5533  (8) νd3p = 71.6835  (9) 1/βRw = 0.7366(10) f2fn/f2 = 0.7177 (11) fF/ft = 0.7832 (12) ωw = 44.7194°

FIG. 17A, FIG. 17B and FIG. 17C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Sixth Example.

FIG. 18A, FIG. 18B and FIG. 18C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Sixth Example.

As is apparent from the above-mentioned graphs showing aberrations, itis understood that the variable magnification optical system relating tothe present Example can correct superbly various aberrations over thewide angle end state to the telephoto end state and has excellentimaging performance, and further has excellent imaging performance evenupon focusing on a close distance object.

Seventh Example

FIG. 19A, FIG. 19B and FIG. 19C are, respectively, cross sectional viewsin a wide angle end state, in an intermediate focal length state and ina telephoto end state, of a variable magnification optical systemaccording to a Seventh Example of the variable magnification opticalsystem of the present embodiment. Arrows below each lens group in FIG.19A show directions of movements of respective lens groups upon varyingmagnification from a wide angle end state to an intermediate focallength state. Arrows below each lens group in FIG. 19B show movementtrajectories of respective lens groups upon varying magnification fromthe intermediate focal length state to the telephoto end state.

The variable magnification optical system according to the presentExample is composed of, in order from an object side along the opticalaxis, a first lens group G1 having positive refractive power, a secondlens group G2 having negative refractive power, an aperture stop S, athird lens group G3 having positive refractive power, and a rear lensgroup GR having positive refractive power.

The first lens group G1 consists of a cemented lens constructed by, inorder from the object side along the optical axis, a negative meniscuslens L11 having a convex surface facing the object side cemented with adouble convex positive lens L12.

The second lens group G2 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L21 having a convexsurface facing the object side, a negative meniscus lens L22 having aconcave surface facing the object side, and a positive meniscus lens L23having a convex surface facing the object side. The negative meniscuslens L21 is a glass mold type aspherical lens whose object side lenssurface and image plane I side lens surface are aspherical.

The third lens group G3 consists of, in order from the object side alongthe optical axis, a positive meniscus lens L31 having a convex surfacefacing the object side, a positive meniscus lens L32 having a convexsurface facing the object side, and a cemented lens constructed by apositive meniscus lens L33 having a convex surface facing the objectside cemented with a negative meniscus lens L34 having a convex surfacefacing the object side. The positive meniscus lens L31 is a glass moldtype aspherical lens whose object side lens surface is aspherical.

The rear lens group GR is composed of, in order from the object sidealong the optical axis, a fourth lens group G4 having positiverefractive power, a fifth lens group G5 having negative refractive powerand a sixth lens group G6 having negative refractive power.

The fourth lens group G4 consists of a double convex positive lens L41.The double convex positive lens L41 is a glass mold type aspherical lenswhose object side lens surface and image plane I side lens surface areaspherical.

The fifth lens group G5 consists of a negative meniscus lens L51 havinga convex surface facing the object side. The negative meniscus lensgroup L51 is a glass mold type aspherical lens whose object side lenssurface is aspherical.

The sixth lens group G6 consists of a negative meniscus lens L61 havinga concave surface facing the object side.

A filter FL such as a low pass filter is disposed between the sixth lensgroup G6 and the image plane I.

On the image plane I, an imaging device (not shown) composed of CCD,CMOS or the like is disposed.

In the variable magnification optical system according to the presentExample, upon varying magnification from the wide angle end state to thetelephoto end state, the first lens group G1, the second lens group G2,the third lens group G3, the fourth lens group G4 and the fifth lensgroup G5, are moved along the optical axis such that a distance betweenthe first lens group G1 and the second lens group G2, a distance betweenthe second lens group G2 and the third lens group G3, a distance betweenthe third lens group G3 and the fourth lens group G4, a distance betweenthe fourth lens group G4 and the fifth lens group G5 and a distancebetween the fifth lens group G5 and the sixth lens group G6 are varied.At this time, the sixth lens group G6 is fixed in its position withrespect to the image plane I. The aperture stop S is moved in a bodywith the third lens group G3 upon varying magnification from the wideangle end state to the telephoto end state.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4 toward theobject along the optical axis as a focusing lens group.

Table 7 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 7 Seventh Example [Surface Data] m r d nd νd OP ∞  1 101.783732.263 1.84666 23.8  2 64.09488 8.457 1.75500 52.3  3 −4649.78570 D3  *4338.09183 2.000 1.85135 40.1 *5 17.62582 9.239  6 −31.88780 1.5001.49782 82.6  7 −480.92591 0.150  8 48.76651 3.362 2.00069 25.5  91462.00720 D9  10(S) ∞ 1.500 *11  40.00000 3.061 1.49710 81.5 12746.47149 0.150 13 56.62003 3.000 1.85896 22.7 14 1991.68980 0.150 1522.31377 3.732 1.49782 82.6 16 102.88645 1.500 1.85896 22.7 17 20.13958D17 *18  25.58334 5.130 1.49710 81.5 *19  −26.20789 D19 *20  44.848571.500 1.74330 49.3 21 19.56479 D21 22 −58.99276 0.839 1.61800 63.3 23−84.99207 21.000 24 1.500 1.51680 64.1 25 ∞ D25 I ∞ [Various Data]Variable magnification ratio 2.75 W M T f 24.72 46.32 67.90 FNo 4.024.01 4.02 ω 43.5 23.3 16.4 Y 21.70 21.70 21.70 TL 115.000 129.999145.678 BF 22.601 22.601 22.602 BF (air converted 22.090 22.090 22.091length) [Lens Group Data] Lens Group ST f 1^(st) Lens Group  1 141.682^(nd) Lens Group  4 −27.31 3^(rd) Lens Group 10 59.45 4^(th) Lens Group18 26.93 5^(th) Lens Group 20 −47.90 6^(th) Lens Group 22 −315.95[Aspherical Surface Data] Surface Number: 4 K = 1.00000e+00 A4 =1.12967e−05 A6 = −4.46018e−08 A8 = 1.00140e−10 A10 = −1.05741e−13Surface Number: 5 K = 0.00000e+00 A4 = 3.44021e−05 A6 = 7.39481e−08 A8 =−2.03619e−10 A10 = 1.51680e−12 Surface Number: 11 K = 1.00000e+00 A4 =−6.99848e−06 A6 = −1.23976e−08 A8 = 1.83746e−10 A10 = −4.96062e−13Surface Number: 18 K = 1.00000e+00 A4 = −1.46574e−05 A6 = 2.12049e−07 A8= −8.82713e−10 A10 = −5.22530e−12 Surface Number: 19 K = 1.00000e+00 A4= 2.32857e−05 A6 = 1.32158e−07 A8 = −5.88648e−10 A10 = −6.83977e−12Surface Number: 20 K = 1.00000e+00 A4 = 4.54779e−06 A6 = −1.12679e−08 A8= −3.81570e−10 A10 = 0.00000e+00 [Variable Distance Data] W M T W M TInfinite Infinite Infinite Close Close Close D3  2.000 22.166 34.5702.000 22.166 34.570 D9  24.510 8.331 2.222 24.510 8.331 2.222 D17 5.9315.867 5.409 4.929 3.275 0.788 D19 4.569 3.472 1.944 5.571 6.063 6.565D21 7.856 20.029 31.398 7.856 20.029 31.398 D25 0.101 0.101 0.102 0.1010.101 0.103 [Values for Conditional Expressions]  (1) f3f/f3r = −0.5270 (2) BFw/fw = 0.9668  (3) f1/fw = 5.7316  (4) βFw = 0.0452  (5) f5/f3 =−0.8058  (6) f1/f1Rw = 6.3640  (7) nd3fp = 1.4971  (8) νd3p = 81.5584 (9) 1/βRw = 0.9286 (10) f2fn/f2 = 0.8021 (11) fF/ft = 0.3965 (12) ωw =43.4833°

FIG. 20A, FIG. 20B and FIG. 20C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Seventh Example.

FIG. 21A, FIG. 21B and FIG. 21C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Seventh Example.

As is apparent from the above-mentioned graphs showing aberrations, itis understood that the variable magnification optical system relating tothe present Example can correct superbly various aberrations over thewide angle end state to the telephoto end state and has excellentimaging performance, and further has excellent imaging performance evenupon focusing on a close distance object.

Eighth Example

FIG. 22A, FIG. 22B and FIG. 22C are, respectively, cross sectional viewsin a wide angle end state, in an intermediate focal length state and ina telephoto end state, of a variable magnification optical systemaccording to an Eighth Example of the variable magnification opticalsystem of the present embodiment. Arrows below each lens group in FIG.22A show directions of movements of respective lens groups upon varyingmagnification from a wide angle end state to an intermediate focallength state. Arrows below each lens group in FIG. 22B show movementtrajectories of respective lens groups upon varying magnification fromthe intermediate focal length state to a telephoto end state.

The variable magnification optical system according to the presentExample is composed of, in order from an object side along the opticalaxis, a first lens group G1 having positive refractive power, a secondlens group G2 having negative refractive power, an aperture stop S, athird lens group G3 having positive refractive power, and a rear lensgroup GR having positive refractive power.

The first lens group G1 consists of a cemented lens constructed by, inorder from the object side along the optical axis, a negative meniscuslens L11 having a convex surface facing the object side cemented with adouble convex positive lens L12.

The second lens group G2 consists of, in order from the object sidealong the optical axis, a negative meniscus lens L21 having a convexsurface facing the object side, a double concave negative lens L22, anda positive meniscus lens L23 having a convex surface facing the objectside. The negative meniscus lens L21 is a glass mold type asphericallens whose image plane I side lens surface is aspherical.

The third lens group G3 consists of, in order from the object side alongthe optical axis, a double convex positive lens L31, a cemented lensconstructed by a negative meniscus lens L32 having a convex surfacefacing the object side cemented with a double convex positive lens L33,and a cemented lens constructed by a positive meniscus lens L34 having aconcave surface facing the object side cemented with a double concavenegative lens L35. The double convex positive lens L31 is a glass moldtype aspherical lens whose object side lens surface is aspherical.

The rear lens group GR is composed of, in order from the object sidealong the optical axis, a fourth lens group G4 having positiverefractive power and a fifth lens group G5 having negative refractivepower.

The fourth lens group G4 consists of, in order from the object sidealong the optical axis, a positive meniscus lens L41 having a convexsurface facing the object side, and a double convex positive lens L42.The double convex positive lens L42 is a glass mold type aspherical lenswhose object side lens surface and image plane I side lens surface areaspherical.

The fifth lens group G5 consists of a cemented lens constructed by, inorder from the object side along the optical axis, a double convexpositive lens L51 and a double concave negative lens L52. The doubleconcave negative lens L52 is a glass mold type aspherical lens whoseobject side lens surface is aspherical.

A filter FL such as a low pass filter is disposed between the fifth lensgroup G5 and the image plane I.

On the image plane I, an imaging device (not shown) composed of CCD,CMOS or the like is disposed.

In the variable magnification optical system according to the presentExample, upon varying magnification from the wide angle end state to thetelephoto end state, all lens groups of the first lens group G1 to thefifth lens group G5 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4,and a distance between the fourth lens group G4 and the fifth lens groupG5, are varied. The aperture stop S is moved in a body with the thirdlens group G3 upon varying magnification from the wide angle end stateto the telephoto end state.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the positive meniscus lens L41 of thefourth lens group G4 toward the object along the optical axis as afocusing lens group.

Table 8 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 8 Eighth Example [Surface Data] m r d nd νd OP ∞  1 116.511742.150 1.84666 23.8  2 68.14169 8.500 1.75500 52.3  3 −1607.21650 D3   4643.64333 2.000 1.85135 40.1 *5 22.47852 12.291  6 −49.00635 1.5001.49782 82.6  7 35.41428 0.100  8 32.93414 4.000 2.00069 25.5  9134.12564 D9  10(S) ∞ 1.500 *11  23.68026 5.000 1.55332 71.7 12−51.23473 1.136 13 87.42815 1.000 1.97484 25.9 14 48.00600 5.000 1.6180063.3 15 −93.41134 1.653 16 −27.67767 4.500 1.61800 63.3 17 −14.252071.000 1.63137 35.1 18 3549.62960 D18 19 34.01132 1.500 1.83858 33.3 2052.01107 6.500 *21  505.55440 4.000 1.59201 67.0 *22  −61.72425 D22 23106.95458 10.000 1.51680 64.1 24 −20.00000 1.500 1.74330 49.3 *25 144.50680 D25 26 ∞ 1.500 1.51680 64.1 27 ∞ D27 1.00000 I ∞ [VariousData] Variable magnification ratio 2.75 W M T f 24.72 46.31 67.89 FNo4.00 4.00 4.00 ω 44.9 23.8 16.5 Y 21.70 21.70 21.70 TL 121.839 134.775154.929 BF 14.062 27.994 39.252 BF (air converted 13.551 27.483 38.741length) [Lens Group Data] Lens Group ST f 1^(st) Lens Group  1 156.612^(nd) Lens Group  4 −26.22 3^(rd) Lens Group 10 38.65 4^(th) Lens Group19 53.93 5^(th) Lens Group 23 −89.77 [Aspherical Surface Data] SurfaceNumber: 5 K = 0.00000e+00 A4 = 1.29856e−05 A6 = 3.72807e−08 A8 =−9.91643e−11 A10 = 5.62653e−13 Surface Number: 11 K = 1.00000e+00 A4 =−6.13337e−06 A6 = 1.52342e−08 A8 = −1.33494e−10 A10 = 5.07280e−13Surface Number: 21 K = 1.00000e+00 A4 = −1.56957e−05 A6 = −4.44053e−08A8 = −8.01823e−10 A10 = −6.52474e−14 Surface Number: 22 K = 1.00000e+00A4 = 6.23173e−06 A6 = −4.75716e−08 A8 = −5.19265e−10 A10 = −1.02402e−13Surface Number: 25 K = 1.00000e+00 A4 = 1.25490e−06 A6 = 3.00760e−08 A8= −1.22687e−10 A10 = 3.40306e−13 [Variable Distance Data] W M T W M TInfinite Infinite Infinite Close Close Close D3  2.000 19.945 36.7442.000 19.945 36.744 D9  20.989 5.771 1.000 20.989 5.771 1.000 D18 4.9142.181 2.103 4.914 2.181 2.103 D22 5.044 4.055 1.000 6.288 6.671 5.279D25 12.462 26.394 37.651 12.462 26.394 37.651 D27 0.100 0.100 0.1010.100 0.100 0.101 [Values for Conditional Expressions]  (1) f3f/f3r =−0.5628  (2) BFw/fw = 0.6275  (3) f1/fw = 6.3354  (4) βFw = 0.7271  (5)f5/f3 = −2.3229  (6) f1/f1Rw = 8.1273  (7) nd3fp = 1.5533  (8) νd3p =71.6835  (9) 1/βRw = 0.8894 (10) f2fn/f2 = 1.0450 (11) fF/ft = 1.3722(12) ωw = 45.6019°

FIG. 23A, FIG. 23B and FIG. 23C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Eighth Example.

FIG. 24A, FIG. 24B and FIG. 24C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Eighth Example.

As is apparent from the above-mentioned graphs showing aberrations, itis understood that the variable magnification optical system relating tothe present Example can correct superbly various aberrations over thewide angle end state to the telephoto end state and has excellentimaging performance, and further has excellent imaging performance evenupon focusing on a close distance object.

According to the above described respective examples, it is possible torealize a variable magnification optical system which is compatible witha large-sized imaging device in spite that the optical system is smallin size, and which can correct superbly various aberrations upon varyingmagnification over the wide angle end state to the telephoto end state,and further has excellent imaging performance even upon focusing on aclose distance object.

Meanwhile, in the variable magnification optical system according to thepresent embodiment, a variable magnification ratio is in the range of 2to 10 times and a 35 mm-size converted focal length in the wide angleend state is in the range of 20 to 30 mm. Further, in the variablemagnification optical system according to the present embodiment, anF-number in the wide angle end state is in the range of about f/2.0 tof/4.5, the F-number in the telephoto end state is in the range of aboutf/2.0 to f/6.3.

Further, each of the above described Examples is a concrete example ofthe present embodiment, and the present embodiment is not limited tothem. The contents described below can be adopted without deterioratingoptical performance of the variable magnification optical systemsaccording to the present embodiment.

Although variable magnification optical systems having a five groupconfiguration or a six group configuration were illustrated above asnumerical examples of the variable magnification optical systemsaccording to the present embodiment, the present embodiment is notlimited to them and variable magnification optical systems having otherconfigurations, such as seven group configuration, or the like, can beconfigured. Concretely, a configuration that a lens or a lens group isadded to the most object side or to the most image side of the variablemagnification optical system according to the each of the abovedescribed Examples is possible. Alternatively, a lens or a lens groupmay be added between the first lens group G1 and the second lens groupG2. Alternatively, a lens or a lens group may be added between thesecond lens group G2 and the third lens group G3. Alternatively, a lensor a lens group may be added between the third lens group G3 and therear lens group GR.

Further, in each of the above described Examples, configurations thatthe rear lens group GR is composed of the fourth lens group G4 and thefifth lens group G5, or of the fourth lens group G4, fifth lens group G5and the sixth lens groups G6, were illustrated, but configurations arenot limited to them.

Further, in each of the above described Examples, a focusing lens groupis composed of one lens group or a part of a lens group, but thefocusing lens group may be composed of two or more lens groups. Autofocusing can be applied for such focusing group(s), and drive by motorfor auto focusing, such as, ultrasonic motor, stepping motor or VCMmotor may be suitably adopted.

Further, in the variable magnification optical systems according to eachof the above described Examples, any lens group in the entirety thereofor a portion thereof can be moved in a direction including a componentperpendicular to the optical axis as a vibration reduction lens group,or rotationally moved (swayed) in an in-plane direction including theoptical axis, whereby a configuration of a vibration reduction can betaken.

Further, in the variable magnification optical systems according to eachof the above described Examples, a lens surface of a lens may be aspherical surface, a plane surface, or an aspherical surface. When alens surface is a spherical surface or a plane surface, lens processing,assembling and adjustment become easy, and it is possible to preventdeterioration in optical performance caused by lens processing,assembling and adjustment errors, so that it is preferable. Moreover,even if an image plane is shifted, deterioration in depictionperformance is little, so that it is preferable. When a lens surface isan aspherical surface, the aspherical surface may be fabricated by agrinding process, a glass molding process that a glass material isformed into an aspherical shape by a mold, or a compound type processthat a resin material is formed into an aspherical shape on a glass lenssurface. A lens surface may be a diffractive optical surface, and a lensmay be a graded-index type lens (GRIN lens) or a plastic lens.

Further, in the variable magnification optical systems according to eachof the above described Examples, it is preferable that the aperture stopS is disposed between the second lens group G2 and the third lens groupG3. But, the function may be substituted by a lens frame withoutdisposing a member as an aperture stop.

Further, the lens surface(s) of the lenses configuring the variablemagnification optical systems according to each of the above describedExamples, may be coated with anti-reflection coating(s) having a hightransmittance in a wide wavelength region. With this contrivance, it isfeasible to reduce a flare as well as ghost and attain excellent opticalperformance with high contrast.

Next, a camera equipped with the variable magnification optical systemaccording to the present embodiment, will be explained with referring toFIG. 25.

FIG. 25 is a view showing a configuration of the camera equipped withthe variable magnification optical system according to the presentembodiment.

The camera 1 as shown in FIG. 25, is a so-called mirror-less camera of alens interchangeable type equipped with the variable magnificationoptical system according to the first Example as an imaging lens 2.

In the present camera 1, a light emitted from an unillustrated object(an object to be photo-taken) is converged by the imaging lens 2,through a unillustrated OLPF (Optical low pass filter), and forms animage of the object on an imaging plane of an image pick-up portion 3.The light from the object is photo-electrically converted through aphoto-electric conversion element provided on the image pick-up portion3 to form a picture image of the object. This picture image is displayedon an EVF (electric view finder) 4 provided on the camera 1.Accordingly, a photographer can observe the object to be photo-takenthrough the EVF.

Further, upon unillustrated release button being depressed by thephotographer, the picture image of the object formed by the imagepick-up portion 3 is stored in an unillustrated memory. Thus, thephotographer can take a photo of the object.

It is noted here that the variable magnification optical system relatingto the First Example in which the present camera 1 is equipped with theimaging lens 2, has superb optical performance as described above and ismade small in size. In other words, the present camera 1 can be madesmall in size and attain superb optical performances that variousaberrations can be corrected well from the wide angle end state to thetelephoto end state and excellent imaging performance is attained evenupon focusing on a close distance object.

Incidentally, when there is configured a camera in which the variablemagnification optical system according to any of the before-mentionedSecond to Eighth Examples is installed as the imaging lens 2, the cameraalso can attain the same effects as those of the above-mentioned camera1. Further, even when the variable magnification optical systemaccording to any of the above Examples is installed in a camera of asingle lens reflex type equipped with a quick return mirror in which theobject image is observed through a finder optical system, the cameraalso can attain the same effects as those of the above-mentioned camera1.

Next, an outline of a method for manufacturing the variablemagnification optical system according to the present embodiment, isdescribed with referring to FIG. 26.

FIG. 26 is a flowchart schematically showing a method for manufacturingthe variable magnification optical system according to the presentembodiment.

The method for manufacturing the variable magnification optical systemaccording to the present embodiment shown in FIG. 26, is a method formanufacturing a variable magnification optical system which comprises,in order from an object side, a first lens group having positiverefractive power, a second lens group having negative refractive power,a third lens group having positive refractive power and a rear lensgroup having positive refractive power; the method comprising thefollowing steps S1 to S3:

Step S1: constructing such that, upon varying a magnification from awide angle end state to a telephoto end state, a distance between thefirst lens group and the second lens group is varied, a distance betweenthe second lens group and the third lens group is varied, and a distancebetween the third lens group and the rear lens group is varied.

Step S2: constructing such that the rear lens group comprises a focusinglens group which is moved upon carrying out focusing from an infinitedistance object to a close distance object.

Step S3: constructing such that the variable magnification opticalsystem satisfies the following conditional expressions (1) and (2):

−1.00<f3f/f3r<−0.0500  (1)

0.100<BFw/fw<1.00  (2)

where f3f denotes a focal length of a most image plane side negativelens component in the third lens group; f3r denotes a composite focallength of lens components disposed on a side which is closer to theobject than the most image plane side negative lens component, in thethird lens group; BFw denotes aback focus of the variable magnificationoptical system in a wide angle end state; and fw denotes a focal lengthof the variable magnification optical system in the wide angle endstate.

According to the above-stated method for manufacturing the variablemagnification optical system according to the present embodiment, it ispossible to realize a variable magnification optical system, while beingdownsized, is compatible with a large-sized imaging device, and whichcan attain superb optical performances that various aberrations can becorrected well over from the wide angle end state to the telephoto endstate and excellent imaging performance is attained even upon focusingon a close distance object.

EXPLANATION OF REFERENCE SYMBOLS

-   -   G1 first lens group    -   G2 second lens group    -   G3 third lens group    -   G4 fourth lens group    -   G5 fifth lens group    -   G6 sixth lens group    -   GR rear lens group    -   S aperture stop    -   I image plane

1. A variable magnification optical system comprises, in order from anobject side, a first lens group having positive refractive power, asecond lens group having negative refractive power, a third lens grouphaving positive refractive power, and a rear lens group having positiverefractive power; upon varying a magnification, a distance between saidfirst lens group and said second lens group being varied, a distancebetween said second lens group and said third lens group being varied,and a distance between said third lens group and said rear lens groupbeing varied; said rear lens group comprising a focusing lens groupwhich is moved upon carrying out focusing; and the following conditionalexpressions being satisfied:−1.00<f3f/f3r<−0.05000.100<BFw/fw<1.00 where f3f denotes a focal length of a most image planeside negative lens component in said third lens group; f3r denotes acomposite focal length of lens components disposed on a side which iscloser to the object than said most image side negative lens component,in said third lens group; BFw denotes a back focus of said variablemagnification optical system in a wide angle end state; and fw denotes afocal length of said variable magnification optical system in the wideangle end state.
 2. A variable magnification optical system according toclaim 1, wherein the following conditional expression is satisfied:2.00<f1/fw<8.000 where f1 denotes a focal length of the first lensgroup, and fw denotes a focal length of the variable magnificationoptical system in the wide angle end state.
 3. A variable magnificationoptical system according to claim 1, wherein the following conditionalexpression is satisfied:0.040<βFw<0.800 where βFw denotes transverse magnification of thefocusing lens group in the wide angle end state.
 4. A variablemagnification optical system according to claim 1, wherein the rear lensgroup comprises a fourth lens group having positive refractive power,and a fifth lens group having negative refractive power, and thefollowing conditional expression is satisfied:−3.000<f5/f3<−0.500 where f3 denotes a focal length of the third lensgroup, and f5 denotes a focal length of the fifth lens group.
 5. Avariable magnification optical system according to claim 4, wherein saidfourth lens group comprises said focusing group.
 6. A variablemagnification optical system according to claim 1, wherein the followingconditional expression is satisfied:4.000<f1/f1Rw<9.000 where f1 denotes a focal length of the first lensgroup, and f1Rw denotes a composite focal length of lens groups in thewide angle end state disposed on the side which is closer to the imageplane than the first lens group.
 7. A variable magnification opticalsystem according to claim 1, wherein the following conditionalexpression is satisfied:nd3fp<1.800 where nd3fp denotes refractive index of a lens having thelargest refractive index in the third lens group.
 8. A variablemagnification optical system according to claim 1, wherein the followingconditional expression is satisfied:50.000<νd3p where νd3p denotes Abbe's number of a lens having thesmallest Abbe's number in the third lens group.
 9. A variablemagnification optical system according to claim 1, wherein the followingconditional expression is satisfied:0.500<1/βRw<1.000 where βRw denotes a transverse magnification of lensgroup disposed at the most image plane side in the wide angle end state.10. A variable magnification optical system according to claim 1,wherein the following conditional expression is satisfied:0.500<f2fn/f2<1.100 where f2fn denotes a focal length of a most objectside lens component in the second lens group, and f2 denotes a focallength of the second lens group.
 11. A variable magnification opticalsystem according to claim 1, wherein the following conditionalexpression is satisfied:0.300<fF/ft<1.400 where fF denotes a focal length of the focusing lensgroup, and ft denotes a focal length of the variable magnificationoptical system in the telephoto end state.
 12. A variable magnificationoptical system according to claim 1, wherein the following conditionalexpression is satisfied:40.00°<ωw<85.00° where ωw denotes a half angle of view of the variablemagnification optical system in the telephoto end state.
 13. An opticalapparatus comprising a variable magnification optical system accordingto claim
 1. 14. A method for manufacturing a variable magnificationoptical system which comprises, in order from an object side, a firstlens group having positive refractive power, a second lens group havingnegative refractive power, a third lens group having positive refractivepower and a rear lens group having positive refractive power; the methodcomprising the following steps: constructing such that, upon varying amagnification, a distance between the first lens group and the secondlens group is varied, a distance between the second lens group and thethird lens group is varied, and a distance between the third lens groupand the rear lens group is varied; constructing such that the rear lensgroup comprises a focusing lens group which is moved upon carrying outfocusing; and constructing such that the following conditionalexpressions are satisfied:−1.00<f3f/f3r<−0.05000.100<BFw/fw<1.00 where f3f denotes a focal length of a most image planeside negative lens component in said third lens group; f3r denotes acomposite focal length of lens components disposed on a side which iscloser to the object than the most image plane side negative lenscomponent, in the third lens group; BFw denotes a back focus of thevariable magnification optical system in a wide angle end state; and fwdenotes a focal length of the variable magnification optical system inthe wide angle end state.